Bluetooth: BT_HCIUART now depends on SERIAL_DEV_BUS

It is no longer possible to build BT_HCIUART into the kernel
when SERIAL_DEV_BUS is a loadable module, even if none of the
SERIAL_DEV_BUS based implementations are selected:

drivers/bluetooth/hci_ldisc.o: In function `hci_uart_set_flow_control':
hci_ldisc.c:(.text+0xb40): undefined reference to `serdev_device_set_flow_control'
hci_ldisc.c:(.text+0xb5c): undefined reference to `serdev_device_set_tiocm'

This adds a dependency to avoid the broken configuration.

Fixes: 7841d554809b ("Bluetooth: hci_uart_set_flow_control: Fix NULL deref when using serdev")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/Kconfig

@@ -65,6 +65,7 @@ config BT_HCIBTSDIO
 
 config BT_HCIUART
 	tristate "HCI UART driver"
+	depends on SERIAL_DEV_BUS || !SERIAL_DEV_BUS
 	depends on TTY
 	help
 	  Bluetooth HCI UART driver.
@@ -79,7 +80,6 @@ config BT_HCIUART
 config BT_HCIUART_SERDEV
 	bool
 	depends on SERIAL_DEV_BUS && BT_HCIUART
-	depends on SERIAL_DEV_BUS=y || SERIAL_DEV_BUS=BT_HCIUART
 	default y
 
 config BT_HCIUART_H4