cosmetic: debug: Replace #ifdef DEBUG with debug() macro

Replace #ifdef DEBUG with dedicated debug() macro.

Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>

common/bootm_os.c

@@ -484,9 +484,8 @@ int boot_selected_os(int argc, char * const argv[], int state,
 	    state == BOOTM_STATE_OS_FAKE_GO) /* We expect to return */
 		return 0;
 	bootstage_error(BOOTSTAGE_ID_BOOT_OS_RETURNED);
-#ifdef DEBUG
-	puts("\n## Control returned to monitor - resetting...\n");
-#endif
+	debug("\n## Control returned to monitor - resetting...\n");
+
 	return BOOTM_ERR_RESET;
 }