Revert previous break changes that return UC_ERR_ARG for non-existing registers

But print a warning instead

qemu/target/s390x/unicorn.c

@@ -80,7 +80,7 @@ uc_err reg_read(void *_env, int mode, unsigned int regid, void *value,
             break;
         }
     }
-
+    CHECK_RET_DEPRECATE(ret, regid);
     return ret;
 }
 
@@ -113,6 +113,7 @@ uc_err reg_write(void *_env, int mode, unsigned int regid, const void *value,
             break;
         }
     }
+    CHECK_RET_DEPRECATE(ret, regid);
     return ret;
 }