Add NMI source Property

System need to keep the NMI signal event source by this Property

Tested
it's tested in system for IPMI OEM command - get/set NMI source

Change-Id: I0f09d30b08540863f65c20315e063916ad620e80
Signed-off-by: Chen Yugang <yugang.chen@linux.intel.com>
1 file changed