wl12xx: update commands & events

Change the commands and events according to the new fw api
(fw >= 6/7.3.0.0.75).

The main change is the replacement of JOIN/DISCONNECT commands,
with ROLE_START/ROLE_STOP commands.

The use of these commands should be preceded by the ROLE_ENABLE
command (allocating role resources), and followed by the
ROLE_DISABLE command (freeing role resources).

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>