Add hci_uart kernel module to linux-rpi2 for the RPi3 on board bcm43xx Bluetooth chipset
This is required to hciattach the bcm43xx to the UART on the RPi3
CONFIG_BT_HCIUART=m
CONFIG_BT_HCIUART_BCM=y
(from redmine: issue id 5619, created on 2016-05-23, closed on 2016-06-02)