Fixes nuttx target warning

```
jerry-main.c: In function 'str_to_uint':
jerry-main.c:89:12: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
   89 |     *out_p = num_str_p;
make[4]: Leaving directory '/home/runner/work/jerryscript/jerryscript/targets/os/nuttx'
make[3]: Leaving directory '/home/runner/work/jerryscript/apps'
```

JerryScript-DCO-1.0-Signed-off-by: Yonggang Luo [email protected]

Author: lygstate

targets/os/nuttx/jerry-main.c

@@ -71,7 +71,7 @@ print_help (char *name)
  */
 static uint32_t
 str_to_uint (const char *num_str_p, /**< string to convert */
-             char **out_p) /**< [out] end of the number */
+             const char **out_p) /**< [out] end of the number */
 {
   assert (jerry_feature_enabled (JERRY_FEATURE_ERROR_MESSAGES));