[AArch64] Let patterns for NEON instructions check runtime mode.

I've had to change:
  HasNEON -> IsNeonAvailable (available only in non-streaming mode)
  HasNEONorSME -> HasNEON    (available in either mode)

In contrast, the Predicate HasSVE (and related) don't need a similar change
because all patterns predicated with HasSVE use scalable vector types, and in
AArch64ISelLowering we've already made sure that none of those type and
operationss are legal if the function is not in the right mode (if it only has
+sme, without +sve).

Author: sdesmalen-arm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -22185,7 +22185,8 @@ static SDValue vectorToScalarBitmask(SDNode *N, SelectionDAG &DAG) {
   ComparisonResult = DAG.getSExtOrTrunc(ComparisonResult, DL, VecVT);
 
   SmallVector<SDValue, 16> MaskConstants;
-  if (VecVT == MVT::v16i8) {
+  if (DAG.getSubtarget<AArch64Subtarget>().isNeonAvailable() &&
+      VecVT == MVT::v16i8) {
     // v16i8 is a special case, as we have 16 entries but only 8 positional bits
     // per entry. We split it into two halves, apply the mask, zip the halves to
     // create 8x 16-bit values, and the perform the vector reduce.