We see the following build failure with CONFIG_BT_HCIUART_NOKIA=y and
CONFIG_BT_HCIUART_H4=n:

drivers/bluetooth/hci_nokia.c: In function 'nokia_recv':
drivers/bluetooth/hci_nokia.c:644:18: error: implicit declaration of function 'h4_recv_buf' [-Werror=implicit-function-declaration]
...

Fix this by selecting the BT_HCIUART_H4 symbol like all the other users
of the protocoll.

Fixes: 7bb31868 ("Bluetooth: add nokia driver")
Signed-off-by: Tobias Regnery <tobias.regnery@gmail.com>
Reviewed-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>