wlcore: protect wlcore_op_set_key with mutex

wlcore_op_set_key() calls wl18xx_set_key(),
which in turn executes some of his function
calls without acquiring wl->mutex and making
sure the fw is awake.

Adding mutex_lock()/ps_elp_wakeup() calls is
not enough, as wl18xx_set_key() calls
wl1271_tx_flush() which can't be called while
the mutex is taken.

Add the required calls to wlcore_op_set_key,
but limit the queues_stop and flushing
to the only encryption types in which
a spare block might be needed (GEM and TKIP).

[Arik - move state != ON check]

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <luca@coelho.fi>