arm64 memcpy+memove 5.10 patch

[Nick Desaulniers]

Dear stable kernel maintainers,
Please consider cherry-picking

commit 6c23d54f4cb8 ("arm64: Import latest memcpy()/memmove() implementation")

to v5.10.y.  It first landed in v5.14-rc1.

It fixes a linkage failure observed when building kernels for ChromeOS
under AutoFDO:

ld.lld: error: arch/arm64/lib/lib.a(memmove.o):(function __memmove:
.text+0x8): relocation R_AARCH64_CONDBR19 out of range: -6331272 is
not in [-1048576, 1048575]; references __memcpy
>>> defined in arch/arm64/lib/lib.a(memcpy.o)

(The prior version of memmove used assembler conditional branches to
memcpy; under AutoFDO the linker will decide where best to place
memmove; it may be > 1MB away from memcpy. After this patch, memcpy
and memmove are the same function).
-- 
Thanks,
~Nick Desaulniers