log_taget_find() should use enum log_target_type, not int

This has shown up in -Wsign-compare

Change-Id: I2f5ba81aa0328db7db29f49f26de4cea3f522789
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index 7907734..4a34c7d 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -431,7 +431,7 @@
 void log_add_target(struct log_target *target);
 void log_del_target(struct log_target *target);
 
-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);
 
 void log_enable_multithread(void);