arm64: patching: implement text_poke API

arm64: patching: implement text_poke API

The text_poke API is used to implement functions like memcpy() and
memset() for instruction memory (RO+X). The implementation is similar to
the x86 version.

This will be used by the BPF JIT to write and modify BPF programs. There
could be more users of this in the future.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240228141824.119877-2-puranjay12@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>