arch/arm: add the Cortex-A78 core

This commit adds the Cortex-A78 core, which is a armv8.2a ISA.
See: [1] [2].

This CPU support was added in GCC 11. See [3] [4].

Buildroot commit 771da1dd9 "configs/nvidia_bf3_defconfig: new
defconfig" [5] added the first defconfig for a board including
this CPU.

[1] https://developer.arm.com/Processors/Cortex-A78
[2] https://developer.arm.com/documentation/101430/0102/Functional-description/Introduction/About-the-core
[3] https://gcc.gnu.org/gcc-11/changes.html
[4] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/aarch64/aarch64-cores.def;hb=releases/gcc-11.1.0#l98
[5] https://gitlab.com/buildroot.org/buildroot/-/commit/771da1dd9b209adfb27d2dd344a4b2fdcc8bacc4

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

arch/Config.in.arm

@@ -466,6 +466,14 @@ config BR2_cortex_a76_a55
 	select BR2_ARM_CPU_HAS_FP_ARMV8
 	select BR2_ARM_CPU_ARMV8A
 	select BR2_ARCH_NEEDS_GCC_AT_LEAST_9
+config BR2_cortex_a78
+	bool "cortex-A78"
+	select BR2_ARM_CPU_HAS_ARM if !BR2_ARCH_IS_64
+	select BR2_ARM_CPU_HAS_NEON if !BR2_ARCH_IS_64
+	select BR2_ARM_CPU_HAS_THUMB2 if !BR2_ARCH_IS_64
+	select BR2_ARM_CPU_HAS_FP_ARMV8
+	select BR2_ARM_CPU_ARMV8A
+	select BR2_ARCH_NEEDS_GCC_AT_LEAST_11
 config BR2_neoverse_n1
 	bool "neoverse-N1 (aka ares)"
 	select BR2_ARM_CPU_HAS_ARM if !BR2_ARCH_IS_64
@@ -876,6 +884,7 @@ config BR2_GCC_TARGET_CPU
 	default "cortex-a75.cortex-a55"	if BR2_cortex_a75_a55
 	default "cortex-a76"	if BR2_cortex_a76
 	default "cortex-a76.cortex-a55"	if BR2_cortex_a76_a55
+	default "cortex-a78"	if BR2_cortex_a78
 	default "neoverse-n1"	if BR2_neoverse_n1
 	default "tsv110"	if BR2_tsv110
 	# armv8.4a