Bluetooth: btmrvl: Do not send vendor events to bluetooth stack

Vendor-specific events shall be processed in driver and not sent
to bluetooth stack where they screw up HCI command countings.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>