Gcc and clang can check format strings of printf-like functions

Since we don't support any other compilers right now, enable that
extension unconditionally.

Fix the bugs found by format string checking.

Corresponding to flashrom svn r1032.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Sean Nelson <audiohacked@gmail.com>

flash.h

@@ -591,7 +591,8 @@ int doit(struct flashchip *flash, int force, char *filename, int read_it, int wr
 #define NT 1    /* Not tested */
 
 /* cli_output.c */
-int print(int type, const char *fmt, ...);
+/* Let gcc and clang check for correct printf-style format strings. */
+int print(int type, const char *fmt, ...) __attribute__((format(printf, 2, 3)));
 #define MSG_ERROR	0
 #define MSG_INFO	1
 #define MSG_DEBUG	2

flashrom.c

@@ -394,7 +394,7 @@ struct shutdown_func_data {
 int register_shutdown(void (*function) (void *data), void *data)
 {
 	if (shutdown_fn_count >= SHUTDOWN_MAXFN) {
-		msg_perr("Tried to register more than %n shutdown functions.\n",
+		msg_perr("Tried to register more than %i shutdown functions.\n",
 			 SHUTDOWN_MAXFN);
 		return 1;
 	}

udelay.c

@@ -91,7 +91,7 @@ void myusec_calibrate_delay(void)
 	msg_pinfo("Calibrating delay loop... ");
 	resolution = measure_os_delay_resolution();
 	if (resolution) {
-		msg_pdbg("OS timer resolution is %u usecs, ", resolution);
+		msg_pdbg("OS timer resolution is %lu usecs, ", resolution);
 	} else {
 		msg_pinfo("OS timer resolution is unusable. ");
 	}