x86, amd_ucode: safeguard against #GP

x86, amd_ucode: safeguard against #GP

When HW tries to load a corrupted patch, it generates #GP
and depending on 'noreboot' parameter on grub, the system
is either stuck in a reboot loop or is hung. Use wrmsr_safe
instead of wrmsrl so that we fail to load microcode gracefully.

Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>