ArmPkg: drop manual ARM programming of generic timer frequency

There is a bit of legacy code in ArmArchTimerLib that attempts to program
the generic timer based on a Pcd. This was only ever done for (32-bit)
ARM in case the cpu lacked the Security Extensions (because if they were
there, Secure firmware would be expected to have configured this before
switching to Non-secure state).

We don't support operation without Secure firmware anymore, but also the
code has been incorrectly invoked only on platforms that *do* implement
the Security Extensions since December 2020 and commit 0dd0d42ab5b6
("ArmPkg: use helper to check for Security extensions in ArmArchTimerLib")

As a result, edk2 has been overriding any programming done by Secure
Firmware on ARM platforms. Which is wrong.

Drop this programming in preparation for deleting the Pcd completely.

Signed-off-by: Leif Lindholm <quic_llindhol@quicinc.com>

ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c

@@ -45,19 +45,6 @@ TimerConstructor (
       // Ref manual, lower bound of the frequency is in the range of 1-10MHz.
       //
       ASSERT (TICKS_PER_MICRO_SEC);
-
- #ifdef MDE_CPU_ARM
-      //
-      // Only set the frequency for ARMv7. We expect the secure firmware to
-      // have already done it.
-      // If the security extension is not implemented, set Timer Frequency
-      // here.
-      //
-      if (ArmHasSecurityExtensions ()) {
-        ArmGenericTimerSetTimerFreq (PcdGet32 (PcdArmArchTimerFreqInHz));
-      }
-
- #endif
     }
 
     //