kernel: Move to Linux v5.4.68-openpower1

This changes the defconfig to make OPAL_I2C=y, so IMA can work
correctly. See the mailing list[1] or the commit message for the
details.

PowerPC related fixes since 5.4.48:

 powerpc/dma: Fix dma_map_ops::get_required_mask
 powerpc/book3s64/radix: Fix boot failure with large amount of guest memory
 vgacon: remove software scrollback support
 powerpc/perf: Fix crashes with generic_compat_pmu & BHRB
 powerpc/perf: Fix soft lockups due to missed interrupt accounting
 powerpc/spufs: add CONFIG_COREDUMP dependency
 powerpc/xive: Ignore kmemleak false positives
 powerpc/64s: Don't init FSCR_DSCR in __init_FSCR()
 powerpc: Fix circular dependency between percpu.h and mmu.h
 powerpc: Allow 4224 bytes of stack expansion for the signal frame
 powerpc/ptdump: Fix build failure in hashpagetable.c
 powerpc/boot: Fix CONFIG_PPC_MPC52XX references
 powerpc/perf: Fix missing is_sier_aviable() during build
 powerpc/book3s64/pkeys: Use PVR check instead of cpu feature
 powerpc/vdso: Fix vdso cpu truncation
 powerpc/rtas: don't online CPUs for partition suspend
 Revert "powerpc/kasan: Fix shadow pages allocation failure"
 powerpc/pseries/svm: Fix incorrect check for shared_lppaca_size
 powerpc/book3s64/pkeys: Fix pkey_access_permitted() for execute disable pkey
 scsi: sr: remove references to BLK_DEV_SR_VENDOR, leave it enabled
 powerpc: Fix kernel crash in show_instructions() w/DEBUG_VIRTUAL
 powerpc/64s/pgtable: fix an undefined behaviour
 powerpc/64s/exception: Fix machine check no-loss idle wakeup
 powerpc/64: Don't initialise init_task->thread.regs
 powerpc/crashkernel: Take "mem=" option into account
 powerpc/perf/hv-24x7: Fix inconsistent output values incase multiple hv-24x7 events run
 powerpc/ptdump: Add _PAGE_COHERENT flag
 powerpc/kasan: Fix stack overflow by increasing THREAD_SHIFT

[1] https://lists.ozlabs.org/pipermail/openpower-firmware/2020-September/000547.html

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/openpower/linux/0004-powerpc-Detect-the-trusted-boot-state-of-the-system.patch b/openpower/linux/0004-powerpc-Detect-the-trusted-boot-state-of-the-system.patch
index 844371d..e2c2c78 100644
--- a/openpower/linux/0004-powerpc-Detect-the-trusted-boot-state-of-the-system.patch
+++ b/openpower/linux/0004-powerpc-Detect-the-trusted-boot-state-of-the-system.patch
@@ -1,7 +1,7 @@
 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
 From: Nayna Jain <nayna@linux.ibm.com>
 Date: Tue, 5 Nov 2019 17:02:07 -0600
-Subject: [PATCH 04/18] powerpc: Detect the trusted boot state of the system
+Subject: [PATCH 04/19] powerpc: Detect the trusted boot state of the system
 
 While secure boot permits only properly verified signed kernels to be
 booted, trusted boot calculates the file hash of the kernel image and