Bluetooth: btmtksdio: use NULL instead of zero

Fix sparse warnings:

drivers/bluetooth/btmtksdio.c:499:57: warning: Using plain integer as NULL pointer
drivers/bluetooth/btmtksdio.c:533:57: warning: Using plain integer as NULL pointer

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
1 file changed