x86, mce: rename mce_notify_user to mce_notify_irq

Rename the mce_notify_user function to mce_notify_irq. The next
patch will split the wakeup handling of interrupt context
and of process context and it's better to give it a clearer
name for this.

Contains a fix from Ying Huang

[ Impact: cleanup ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>