[PATCH] libertas: fix WPA associations by handling ENABLE_RSN correctly

Don't clobber the firmware's internal state machine by setting
ENABLE_RSN more than once during the 4-way handshake.  Check what
the ENABLE_RSN status is and only set if it should be changed.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>