[ARM][MVE] Tail-predication: predicate new elementcount checks on force-enabled

Additional sanity checks were added to get.active.lane.mask's second argument,
the loop tripcount/elementcount, in rG635b87511ec3. Like the other (overflow)
checks, skip this if tail-predication is forced.

Differential Revision: https://reviews.llvm.org/D87769

llvm/lib/Target/ARM/MVETailPredication.cpp

@@ -411,7 +411,7 @@ bool MVETailPredication::IsSafeActiveMask(IntrinsicInst *ActiveLaneMask,
                  << TC2 << " from get.active.lane.mask\n");
       return false;
     }
-  } else {
+  } else if (!ForceTailPredication) {
     // Smoke tests if the element count is a runtime value. I.e., this isn't
     // fully generic because that would require a full SCEV visitor here. It
     // would require extracting the variable from the elementcount SCEV