remove mca-pentium

This patch removes the mca-pentium boot option that was a noop.

besides the source code cleanup factor, this saves some text as well:

   arch/x86/kernel/cpu/bugs.o:
      text    data     bss     dec     hex filename
       651      77       4     732     2dc bugs.o.before
       631      53       4     688     2b0 bugs.o.after

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>