staging: wilc1000: remove wilc_set_machw_change_vir_if

wilc_set_machw_change_vir_if is not used anymore since we use one unified
firmware. Instead, wilc_set_operation_mode is called when wilc_mac_open to
let the wilc use the proper firmware. Remove wilc_set_machw_change_vir_if
and it's functions calls.
In the later patch, mac index will be passed to wilc device.

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