wl1251: enforce changed hw encryption support on monitor state change

The firmware doesn't support per packet encryption selection, so disable hw
encryption support completely while a monitor interface is present to support
injection of packets (which shouldn't get encrypted by hw).
To enforce the changed hw encryption support force a disassociation on
non-monitor interfaces.
For disassociation a workaround using hw connection monitor is employed,
which temporary enables hw connection manager flag.

Signed-off-by: David Gnedt <david.gnedt@davizone.at>
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>