staging: wilc1000: free allocated memory after processing wilc_send_config_pkt()

Free allocated memory after completing wilc_send_config_pkt() function.
Remove unncessary use of 'stamac' pointer in handle_get_inactive_time().

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