phal: Added proc-pre-poweroff support

Changes:
-Adding new service which will be called during
chassis poweroff.

Test:
-Did poweroff to check, if the service file
is getting picked up or not and new added
procedure is getting called.

Signed-off-by: Chirag Sharma <chirshar@in.ibm.com>
Signed-off-by: Ramesh Iyyar <rameshi1@in.ibm.com>
Change-Id: Ic533433c4771216e5681b61cccf154f7ed029457
8 files changed