x86/mce: Kill drain_mcelog_buffer()

This used to flush out MCEs logged during early boot and which
were in the MCA registers from a previous system run. No need
for that now, since we've moved to a genpool.

Suggested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1439396985-12812-7-git-send-email-bp@alien8.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>