x86/microcode/AMD: Shorten function parameter's name

The whole driver calls this "mc", do that here too.

No functionality change.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170120202955.4091-6-bp@alien8.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>