[Backport to 17] [NFC] Use hasAlignment helper (#2856)

Handle all queries of `Alignment` decorations through one and the same
helper function.

(cherry picked from commit 6768532)

lib/SPIRV/SPIRVReader.cpp

@@ -3087,7 +3087,7 @@ void SPIRVToLLVM::transFunctionAttrs(SPIRVFunction *BF, Function *F) {
     if (BA->hasDecorate(DecorationMaxByteOffset, 0, &MaxOffset))
       Builder.addDereferenceableAttr(MaxOffset);
     SPIRVWord AlignmentBytes = 0;
-    if (BA->hasDecorate(DecorationAlignment, 0, &AlignmentBytes))
+    if (BA->hasAlignment(&AlignmentBytes))
       Builder.addAlignmentAttr(AlignmentBytes);
     I->addAttrs(Builder);
   }