staging: speakup: Add __printf format/arg verification, fix fallout

Using __printf allows the compiler to verify formats and arguments.
Use it and fix the single misuse found.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/main.c

@@ -775,7 +775,7 @@ static void say_line(struct vc_data *vc)
 		cp = buf;
 		while (*cp == SPACE)
 			cp++;
-		synth_printf("%d, ", (cp - buf) + 1);
+		synth_printf("%zd, ", (cp - buf) + 1);
 	}
 	spk_punc_mask = spk_punc_masks[spk_reading_punc];
 	spkup_write(buf, i);

drivers/staging/speakup/spk_priv.h

@@ -63,6 +63,7 @@ void spk_do_catch_up(struct spk_synth *synth);
 void spk_synth_flush(struct spk_synth *synth);
 int spk_synth_is_alive_nop(struct spk_synth *synth);
 int spk_synth_is_alive_restart(struct spk_synth *synth);
+__printf(1, 2)
 void synth_printf(const char *buf, ...);
 int synth_request_region(unsigned long start, unsigned long n);
 int synth_release_region(unsigned long start, unsigned long n);