usb: gadget: storage: strict coversion of 'ro' parameter

Bring a strict way to get the 'ro' parameter from the user.

The patch followed by this one adds another boolean parameter. To be consistent
Michał Nazarewicz proposed to use simple_strtol() in both cases (correspondend
discussion in LKML [1]). Due to simple_strtol() doesn't return error in a good
way and we have a boolean parameter the strict_strtoul() is used.

[1] http://lkml.org/lkml/2010/7/14/169

Signed-off-by: Andy Shevchenko <[e-mail]>
Acked-by: Alan Stern <[e-mail]>
Cc: David Brownell <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/storage_common.c

···
 	ssize_t		rc = count;
 	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
 	struct rw_semaphore	*filesem = dev_get_drvdata(dev);
-	int		i;
+	unsigned long	ro;
 
-	if (sscanf(buf, "%d", &i) != 1)
+	if (strict_strtoul(buf, 2, &ro))
 		return -EINVAL;
 
 	/*
···
 		LDBG(curlun, "read-only status change prevented\n");
 		rc = -EBUSY;
 	} else {
-		curlun->ro = !!i;
-		curlun->initially_ro = !!i;
+		curlun->ro = ro;
+		curlun->initially_ro = ro;
 		LDBG(curlun, "read-only status set to %d\n", curlun->ro);
 	}
 	up_read(filesem);