Fix MSVC "result of 32-bit shift implicitly converted to 64 bits" warning. NFC.

Author: RKSimon

llvm/lib/Object/COFFObjectFile.cpp

@@ -2012,7 +2012,7 @@ bool Arm64XRelocRef::operator==(const Arm64XRelocRef &Other) const {
 uint8_t Arm64XRelocRef::getEntrySize() const {
   switch (getType()) {
   case COFF::IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE:
-    return (1u << getArg()) / sizeof(uint16_t) + 1;
+    return (1ull << getArg()) / sizeof(uint16_t) + 1;
   case COFF::IMAGE_DVRT_ARM64X_FIXUP_TYPE_DELTA:
     return 2;
   default: