Marvell: RealTimeClockLib: Rework LibGetWakeupTime/LibSetWakeupTime

Apply multiple fixes to the Marvell RealTimeClockLib wakeup
library callbacks.

LibGetWakeupTime:
* Add input parameters validation
* Fix 'Pending' value check

LibSetWakeupTime:
* Allow disabling the wakeup timer regardless the input 'Time' value
* Use more generic 'Time' value verification, which is more strict
  than the replaced custom one.
* Use proper alarm mask for 'Pending' signalling

With above the ACS3.0 FWTS and SCT timer tests pass cleanly.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>