Bluetooth: Add opcode to error message

Sometimes HCI command sending timeouts and gives error message without
specifying which command causes error. Patch makes sure that opcode
is printed to help debugging.

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