[bluetooth-next:master 12/21] hci_ldisc.c:undefined reference to `serdev_device_set_flow_control'

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git master
head:   0435605289298a7311f78d02eb6a015cae7dbaf7
commit: 7841d554809b518a22349e7e39b6b63f8a48d0fb [12/21] Bluetooth: hci_uart_set_flow_control: Fix NULL deref when using serdev
config: x86_64-randconfig-v0-10071311 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout 7841d554809b518a22349e7e39b6b63f8a48d0fb
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/bluetooth/hci_ldisc.o: In function `hci_uart_set_flow_control':

quoted

hci_ldisc.c:(.text+0x1b45): undefined reference to `serdev_device_set_flow_control'
hci_ldisc.c:(.text+0x1b89): undefined reference to `serdev_device_set_tiocm'

   hci_ldisc.c:(.text+0x1ba2): undefined reference to `serdev_device_set_tiocm'

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