x86, mce: fix comment style in mce-inject.c

Fix style of winged comment in mce-inject.c.

[ Impact: comment only ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>