msm: ssr: Add sysfs entry to show number of subsystem crashes

Add a sysfs entry in the subsys* directory for each subsystem
called 'crash_count'. This entry gives the number of times that
a subsystem has crashed in the time that the device has been on.

Change-Id: I234b9dfb0fd59bce4ca19180c5c3d6452098488b
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>