arm64: efi: Add missing Kconfig dependency on KERNEL_MODE_NEON

The EFI runtime services ABI permits calls to EFI to clobber
certain FPSIMD/NEON registers, as per the AArch64 procedure call
standard.

Saving/restoring the clobbered registers around such calls needs
KERNEL_MODE_NEON, but the dependency is missing from Kconfig.

This patch adds the missing dependency.

This will aid bisection of the patches implementing support for the
ARM Scalable Vector Extension (SVE).
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/Kconfig

@@ -1064,6 +1064,7 @@ config EFI_STUB
 config EFI
 	bool "UEFI runtime support"
 	depends on OF && !CPU_BIG_ENDIAN
+	depends on KERNEL_MODE_NEON
 	select LIBFDT
 	select UCS2_STRING
 	select EFI_PARAMS_FROM_FDT