ArmPlatformPkg,ArmVirtPkg: delete redundant PL031 functions

Remove the functions now provided by TimeBaseLib from
PL031RealTimeClockLib. Add TimeBaseLib resolution to ArmVirtPkg
in same commit to prevent breakage.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>