wl12xx: declare support for hw scan while idle

By allowing hw scan while idle, we no longer
need the redundant ROC/CROC that are done
on idle off/on, which helps simplifying the
state machine of the driver.

This way, we can also allow scanning while
there is an ongoing sched scan (otherwise,
we won't be able to ROC on idle-off)

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