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 <[e-mail]>
Signed-off-by: Jiapeng Chong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/ataflop.c

···
 	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;