block: ataflop: Fix warning comparing pointer to 0

Fix the following coccicheck warning:

./drivers/block/ataflop.c:1464:20-21: WARNING comparing pointer to 0.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/1635501029-81391-1-git-send-email-jiapeng.chong@linux.alibaba.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ataflop.c

@@ -1460,8 +1460,7 @@ static int floppy_revalidate(struct gendisk *disk)
 	unsigned int drive = p - unit;
 
 	if (test_bit(drive, &changed_floppies) ||
-	    test_bit(drive, &fake_change) ||
-	    p->disktype == 0) {
+	    test_bit(drive, &fake_change) || !p->disktype) {
 		if (UD.flags & FTD_MSG)
 			printk(KERN_ERR "floppy: clear format %p!\n", UDT);
 		BufferDrive = -1;