x86/mce: Don't print MCEs when mcelog is active

Since:

  cd9c57ca

 ("x86/MCE: Dump MCE to dmesg if no consumers")

all MCEs are printed even when mcelog is running. Fix the regression to
not print to dmesg when mcelog is running as it is a consumer too.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
[ Massage commit message. ]
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>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: stable@vger.kernel.org # 4.10..
Fixes: cd9c57ca

 ("x86/MCE: Dump MCE to dmesg if no consumers")
Link: http://lkml.kernel.org/r/20170327093304.10683-2-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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