x86, microcode: Share native MSR accessing variants

We want to use those in AMD's early loading path too. Also, add a
native_wrmsrl variant.

Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>

diff --cc arch/x86/include/asm/microcode.h
Simple merge

diff --cc arch/x86/kernel/microcode_intel_early.c
Simple merge