[TableGen] Update comment for size of NumToSkip field in DecoderEmitter. NFC

NumToSkip is 24 bits. It used to be 16 bits.

Author: topperc

llvm/utils/TableGen/DecoderEmitter.cpp

@@ -681,7 +681,7 @@ static void resolveTableFixups(DecoderTable &Table, const FixupList &Fixups,
   for (FixupList::const_reverse_iterator I = Fixups.rbegin(), E = Fixups.rend();
        I != E; ++I) {
     // Calculate the distance from the byte following the fixup entry byte
-    // to the destination. The Target is calculated from after the 16-bit
+    // to the destination. The Target is calculated from after the 24-bit
     // NumToSkip entry itself, so subtract two  from the displacement here
     // to account for that.
     uint32_t FixupIdx = *I;