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

But print a warning instead

qemu/unicorn_common.h

@@ -154,4 +154,16 @@ static inline void uc_common_init(struct uc_struct* uc)
     ret = UC_ERR_OK;                          \
 } while(0)
 
+#define CHECK_RET_DEPRECATE(ret, regid) do {                                         \
+    if (ret == UC_ERR_ARG && !getenv("UC_IGNORE_REG_BREAK")) {                  \
+        fprintf(stderr,                                                         \
+        "WARNING: Your register accessing on id %"PRIu32" is deprecated"        \
+        " and will get UC_ERR_ARG in the future release (2.2.0) because"        \
+        " the accessing is either no-op or not defined."                        \
+        " Set UC_IGNORE_REG_BREAK=1 to ignore this warning.\n",                 \
+        regid);                                                                 \
+        ret = UC_ERR_OK;                                                        \
+    }                                                                           \
+} while (0)
+
 #endif