usb: gadget: f_mass_storage: Fix the logic to iterate all common->luns

It is wrong to do --i in the for loop.

Fixes: dd02ea5a3305 ("usb: gadget: mass_storage: Use static array for luns")
Signed-off-by: Axel Lin <[e-mail]>
Reviewed-by: Krzysztof Opasiak <[e-mail]>
Acked-by: Michal Nazarewicz <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/function/f_mass_storage.c

···
 		int i;
 
 		down_write(&common->filesem);
-		for (i = 0; i < ARRAY_SIZE(common->luns); --i) {
+		for (i = 0; i < ARRAY_SIZE(common->luns); i++) {
 			struct fsg_lun *curlun = common->luns[i];
 			if (!curlun || !fsg_lun_is_open(curlun))
 				continue;