x86/microcode/intel: Improve microcode sanity-checking error messages

Turn them into proper sentences. Add comments to microcode_sanity_check() to
explain what it does.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1457345404-28884-5-git-send-email-bp@alien8.de


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