staging: wilc1000: use 'struct' to pack cfg header frame in wilc_wlan_cfg_commit()

Make use of 'struct' to pack cfg header in wilc_wlan_cfg_commit()
instead of byte by byte filling.

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