Adds support for extended window size (EWS) config option. We enable EWS
feature in L2CAP Info RSP when hs enabled. EWS option is included in L2CAP
Config Req if tx_win (which is set via socket) bigger then standard default
value (63) && hs enabled && remote side supports EWS feature.

Using EWS selects extended control field in L2CAP.

Code partly based on Qualcomm and Atheros patches sent upstream a year ago.
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>