Fix logic in ldr_ro_manager

Fix argument type for isdigit/isxdigit

stratosphere/pm/source/pm_boot2.cpp

@@ -32,7 +32,7 @@
 
 static bool IsHexadecimal(const char *str) {
     while (*str) {
-        if (isxdigit(*str)) {
+        if (isxdigit((unsigned char)*str)) {
             str++;
         } else {
             return false;