Bluetooth: hci_uart: Update Broadcom UART setup

Use btbcm helpers to perform controller setup.
Perform host UART reset to init speed between btbcm_patchram() and
btbcm_finalize(). This may be need because firmware loading may have
reseted controller UART to init speed.

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>