[llvm][NFC] Update LocalVarDef::CVRegister to fix size MS ABI (#140214)

LocalVarDef::CVRegister being a uint16_t is not enough for the fields to
be packed with the MS ABI.

This makes the field a 16 bit a uint32_t

Author: ojhunt

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h

@@ -70,7 +70,7 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
     /// Register containing the data or the register base of the memory
     /// location containing the data.
-    uint16_t CVRegister;
+    uint32_t CVRegister : 16;
 
     uint64_t static toOpaqueValue(const LocalVarDef DR) {
       uint64_t Val = 0;