Bluetooth: btmtkuart: Improve exception handling in btmtuart_probe()

Calls of the functions clk_disable_unprepare() and hci_free_dev()
were missing for the exception handling.
Thus add the missed function calls together with corresponding
jump targets.

Fixes: 05582561

 ("Bluetooth: btmtkuart: add an implementation for clock osc property")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>