kernel: Move to Linux v5.4.48-openpower1

This adds secure boot support backported from upstream and enables it
in the configuration.

Appearing in the backports is a patch to disable STRICT_KERNEL_RWX so
it drops out of the configuration.

Backported patches to support secureboot:

 powerpc/ima: Fix secure boot rules in ima arch policy
 powerpc/ima: Indicate kernel modules appended signatures are enforced
 powerpc/xmon: Allow listing and clearing breakpoints in read-only mode
 powerpc: Load firmware trusted keys/hashes into kernel keyring
 x86/efi: move common keyring handler functions to new file
 powerpc: expose secure variables to userspace via sysfs
 powerpc/powernv: Add OPAL API interface to access secure variable
 powerpc/ima: Update ima arch policy to check for blacklist
 ima: Check against blacklisted hashes for files with modsig
 certs: Add wrapper function to check blacklisted binary hash
 ima: Make process_buffer_measurement() generic
 powerpc/ima: Define trusted boot policy
 powerpc: Detect the trusted boot state of the system
 powerpc/ima: Add support to initialize ima policy rules
 powerpc: Detect the secure boot mode of the system

PowerPC related fixes:

 powerpc/64s: Save FSCR to init_task.thread.fscr after feature init
 powerpc/64s: Don't let DT CPU features set FSCR_DSCR
 powerpc/kasan: Fix shadow pages allocation failure
 powerpc/kasan: Fix issues by lowering KASAN_SHADOW_END
 powerpc/fadump: Account for memory_limit while reserving memory
 powerpc/fadump: consider reserved ranges while reserving memory
 powerpc/fadump: use static allocation for reserved memory ranges
 powerpc/mm: Fix conditions to perform MMU specific management by blocks on PPC32.
 powerpc/spufs: fix copy_to_user while atomic
 sched/core: Fix illegal RCU from offline CPUs
 powerpc/ptdump: Properly handle non standard page size
 powerpc/xive: Clear the page tables for the ESB IO mapping
 bpf: Support llvm-objcopy for vmlinux BTF
 powerpc/xmon: Restrict when kernel is locked down
 powerpc/powernv: Avoid re-registration of imc debugfs directory
 powerpc/64s: Disable STRICT_KERNEL_RWX
 powerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLE
 powerpc/mm: Fix CONFIG_PPC_KUAP_DEBUG on PPC32
 powerpc/kuap: PPC_KUAP_DEBUG should depend on PPC_KUAP
 powerpc/setup_64: Set cache-line-size based on cache-block-size
 Revert "powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled"

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch b/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
index 5879598..dc4afac 100644
--- a/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
+++ b/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
@@ -1,7 +1,7 @@
 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
 From: Brian King <brking@linux.vnet.ibm.com>
 Date: Wed, 25 Oct 2017 10:42:59 +1100
-Subject: [PATCH 1/2] xhci: Reset controller on xhci shutdown
+Subject: [PATCH 01/18] xhci: Reset controller on xhci shutdown
 
 Fixes kexec boot. Without a hard reset, some USB chips will fail to
 initialize in a kexec booted kernel.
@@ -14,7 +14,7 @@
  1 file changed, 3 insertions(+)
 
 diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
-index 2f49a7b3ce85..b7e17c62396e 100644
+index 81b54a3d2910..b0f66b42a16a 100644
 --- a/drivers/usb/host/xhci.c
 +++ b/drivers/usb/host/xhci.c
 @@ -789,6 +789,9 @@ void xhci_shutdown(struct usb_hcd *hcd)