toshiba_bluetooth: Clean up *_add function and disable BT device at removal

This patch cleans the toshiba_bluetooth_add function by using the
recently introduced function toshiba_bluetooth_present, simplifying
its code and returning appropriate error values.

Also, disables the BT device at the removal of the driver, by using
the function toshiba_bluetooth_disable.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>