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/configs/opal_defconfig b/openpower/configs/opal_defconfig
index 9a74eb4..3fa62fb 100644
--- a/openpower/configs/opal_defconfig
+++ b/openpower/configs/opal_defconfig
@@ -13,7 +13,7 @@
 BR2_ROOTFS_POST_BUILD_SCRIPT="../openpower/scripts/fixup-target-var ../openpower/scripts/firmware-whitelist"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.4.48"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.4.68"
 BR2_LINUX_KERNEL_PATCH="$(BR2_EXTERNAL_OP_BUILD_PATH)/linux"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="$(BR2_EXTERNAL_OP_BUILD_PATH)/configs/linux/skiroot_defconfig"