staging: wilc1000: remove function pointer rx_complete

just call the function linux_wlan_rx_complete directly. No need for a pointer
to the functions. Remove rx_complete, wilc_wlan_net_func_t and net_func which
are not used anymore.
Finally remove static from the function linux_wlan_rx_complete.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>