nmi: x86: convert to generic nmi handler

Convert x86 to use the generic nmi handler code which can be shared
between architectures.

Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --cc arch/x86/kernel/apic/hw_nmi.c
Simple merge