fix(misc): Remove duplicate declaration of _lv_log_add. (lvgl#3103)

Commit ba38a4b appears to have accidentally added a duplicate declaration of
_lv_log_add. With -Wredundant-decls, this causes warnings to spam the terminal.

    warning: redundant redeclaration of ‘_lv_log_add’ [-Wredundant-decls]

Author: jasonpritchard

src/misc/lv_log.h

@@ -71,18 +71,6 @@ void lv_log_register_print_cb(lv_log_print_g_cb_t print_cb);
  */
 void lv_log(const char * format, ...) LV_FORMAT_ATTRIBUTE(1, 2);
 
-/**
- * Add a log
- * @param level     the level of log. (From `lv_log_level_t` enum)
- * @param file      name of the file when the log added
- * @param line      line number in the source code where the log added
- * @param func      name of the function when the log added
- * @param format    printf-like format string
- * @param ...       parameters for `format`
- */
-void _lv_log_add(lv_log_level_t level, const char * file, int line,
-                 const char * func, const char * format, ...) LV_FORMAT_ATTRIBUTE(5, 6);
-
 /**
  * Add a log
  * @param level     the level of log. (From `lv_log_level_t` enum)