refactor: changes to support both instances of SP805

The helper functions are modified to take an additional argument
which specifies the base address of SP805 watchdog module. In the
subsequent patch, we add support for Trusted watchdog module.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Ibfd394fd85092b5e3543db9a476cd636026fa55b
1 file changed