staging: wilc1000: wilc_wlan.c: remove unused pointer variables

This patch removes unused two pointer variable.
 - Free_head
 - Alloc_head
It's pointer variables unused inside code.

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