brd: Switch rd_size to unsigned long

Currently rd_size was int which lead to overflow and bogus device size
once the requested ramdisk size was 1 TB or more. Although these days
ramdisks with 1 TB size are mostly a mistake, the days when they are
useful are not far.
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/brd.c

@@ -443,8 +443,8 @@ static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
 module_param(rd_nr, int, S_IRUGO);
 MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
 
-int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
-module_param(rd_size, int, S_IRUGO);
+unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_size, ulong, S_IRUGO);
 MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
 
 static int max_part = 1;