log_taget_find() should use enum log_target_type, not int

This has shown up in -Wsign-compare

Change-Id: I2f5ba81aa0328db7db29f49f26de4cea3f522789
diff --git a/src/logging.c b/src/logging.c
index 7f6dbb5..9d2a065 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -1259,7 +1259,7 @@
  *  \returns Log target (if found), NULL otherwise
  *  Must be called with mutex osmo_log_tgt_mutex held, see log_tgt_mutex_lock.
  */
-struct log_target *log_target_find(int type, const char *fname)
+struct log_target *log_target_find(enum log_target_type type, const char *fname)
 {
 	struct log_target *tgt;