logging: remove log_initialized(void)

This function does not exist, and was apparently accidentally added (?)
to the header.

Change-Id: I479ef8484506ff27918df9fbf6cbeda8b304bbaa
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index 5ae38c7..755564d 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -399,7 +399,6 @@
 				__attribute__ ((format (printf, 6, 7)));
 void logp_stub(const char *file, int line, int cont, const char *format, ...);
 int log_init(const struct log_info *inf, void *talloc_ctx);
-int log_initialized(void);
 void log_fini(void);
 int log_check_level(int subsys, unsigned int level);