Bluetooth: Initialize the transmit queue for L2CAP streaming mode

Commit 105bdf9e introduced a
regression in L2CAP streaming mode due to rearranged initialization
code that is shared between ERTM and streaming mode.  This change
makes sure the transmit queue is initialized in both modes.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Acked-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo@padovan.org>