Bluetooth: btmtksdio: Fix PM runtime reference leak in shutdown

In btmtksdio_shutdown(), pm_runtime_get_sync() is called at the
beginning of the function.  However, if sending the WMT function
control command fails later, the driver returns early.

It bypasses the corresponding pm_runtime_put_noidle() and
pm_runtime_disable() calls, leaking the PM usage counter and leaving PM
runtime enabled indefinitely.

Fall through to execute the PM runtime cleanup block even if WMT errors.

Fixes: 7f3c563c575e ("Bluetooth: btmtksdio: Add runtime PM support to SDIO based Bluetooth")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>