staging: wilc1000: replace kmalloc with kzalloc

This patch replaces kmalloc with kzalloc because it is initialized by 0
immediately after allcating memory.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>