Bluetooth: Set txwin values for streaming mode

The transmit window values must be configured for streaming mode, even
though streaming mode does not have a window.  This enables use of
extended headers when the transmit window socket option is set to 64
or larger.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>