PcdArmArchTimerFreqInHz lets platforms override the architectural timer
frequency, but this really isn't supported in hardware by anything lower
than EL3. And we no longer support running edk2 at EL3.
So drop this Pcd and update ArmArchTimerLib to unconditionally use
ArmGenericTimerGetTimerFreq () instead.
Signed-off-by: Leif Lindholm <quic_llindhol@quicinc.com>
