staging: wilc1000: handle tx power related callback from cfg80211 context

Avoid the use of internal work queue to defer the handling of tx power
related cfg operations callback. Now issuing the wid command to firmware
directly from the caller context.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>