staging: wilc1000: remove struct del_beacon

This patch removes struct del_beacon which is not necessary. This patch
also changes Handle_DelBeacon function by removing 2nd parameter, struct
del_beacon because it is not used inside.

Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>