[llvm-size] Initialize Radix to correct value (#128447)

Without the patch, invalid --radix, makes Radix to be 0, and result
in invalid format specifier ` %#7 `, instead of e.g ` %#7x `.

Author: vitalybuka

llvm/tools/llvm-size/llvm-size.cpp

@@ -76,7 +76,7 @@ static std::vector<StringRef> ArchFlags;
 static bool ELFCommons;
 static OutputFormatTy OutputFormat;
 static bool DarwinLongFormat;
-static RadixTy Radix;
+static RadixTy Radix = RadixTy::decimal;
 static bool TotalSizes;
 
 static std::vector<std::string> InputFilenames;