usb: mass-storage: Build warning fixes for 64-bit

Fix a printf format mismatch warning seen on 64-bit builds.

Cc: Ɓukasz Majewski <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Lukasz Majewski <l.majewski@samsung.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index e045957..71fd49d 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -973,7 +973,7 @@
 
 			/* If an error occurred, report it and its position */
 			if (nwritten < amount) {
-				printf("nwritten:%d amount:%d\n", nwritten,
+				printf("nwritten:%zd amount:%u\n", nwritten,
 				       amount);
 				curlun->sense_data = SS_WRITE_ERROR;
 				curlun->info_valid = 1;