WEXT: Add support for passing PMK and capability flags to WEXT

This defines the flags for setting the PMK to the driver and the
capability flag for this so that the user space program can figure out
whether the target driver wants to do 4-way hand shake by itself and
pass the PMK which is needed before 4-way handshake to the driver.

Signed-off-by: Masakazu Mokuno <mokuno@sm.sony.co.jp>
Signed-off-by: John W. Linville <linville@tuxdriver.com>