fix(zynqmp): initialize uint32 with value 0U in pm code

fix(zynqmp): initialize uint32 with value 0U in pm code

MISRA Violation: MISRA C-2012 Rule 7.2
- Initialize the unsigned int with value 0u in pm_service component.

Current misra warning detection tool is not reporting this as
warning. It reports only when the initialized value exceeds the
range of data type based on compiler used.

But, this change is added as a part of precaution as some other
misra checker tool may report it as violation of rule 7.2.

Signed-off-by: Naman Patel <naman.patel@amd.com>
Change-Id: I50a5cee2a077fe157e79757d959ce33064225af3