MdePkg/BaseRngLib AARCH64: Remove overzealous ASSERT()

BaseRngLib on AARCH64 will discover whether or not RNDR instructions are
supported, by inspecting the ISAR0 identification register, and setting
a global boolean accordingly. This boolean is used in subsequent
execution to decide whether or not to issue the instruction.

The same discovery code also ASSERT()s that RNDR instructions are
implemented, which is unnecessary, and breaks execution on systems that
incorporate the library but don't implement the instruction (or fail to
expose it to the exception level that the firmware executes at).

So drop the ASSERT().

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>

Committed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Doug Flick [MSFT] <doug.edk2@gmail.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdePkg/Library/BaseRngLib/AArch64/Rndr.c

@@ -50,7 +50,6 @@ BaseRngLibConstructor (
   // MSR. A non-zero value indicates that the processor supports the RNDR instruction.
   //
   Isar0 = ArmReadIdIsar0 ();
-  ASSERT ((Isar0 & RNDR_MASK) != 0);
 
   mRndrSupported = ((Isar0 & RNDR_MASK) != 0);