staging: wilc1000: use kmemdup instead of kmalloc/memcpy

This patch replaces kmalloc followed by memcpy with kmemdup.
It is also added error checking to return -ENOMEM when kmemdup is
failed.

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