x86: coding style fixes for nmi.c

before
	total: 1 errors, 6 warnings, 534 lines checked
after
	total: 0 errors, 1 warnings, 532 lines checked

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>