[SPIR-V][NFC] More efficient getPaddedLen (#105823)

Quick fix with small performance improvement for getPaddedLen function.

Author: bwlodarcz

llvm/lib/Target/SPIRV/SPIRVUtils.cpp

@@ -45,10 +45,7 @@ static uint32_t convertCharsToWord(const StringRef &Str, unsigned i) {
 }
 
 // Get length including padding and null terminator.
-static size_t getPaddedLen(const StringRef &Str) {
-  const size_t Len = Str.size() + 1;
-  return (Len % 4 == 0) ? Len : Len + (4 - (Len % 4));
-}
+static size_t getPaddedLen(const StringRef &Str) { return Str.size() + 4 & ~3; }
 
 void addStringImm(const StringRef &Str, MCInst &Inst) {
   const size_t PaddedLen = getPaddedLen(Str);