Staging: wilc1000: Replace memcpy by ether_addr_copy

This patch fixes the following checkpatch.pl warning: Prefer

ether_addr_copy() over memcpy() if the Ethernet addresses are
__aligned(2)

According to ether_addr_copy() description and functionality, all
Ethernet addresses should align to the u16 datatype.

Here is the output of pahole for the relevant datastructures:
struct del_sta {
	u8                         mac_addr[6];          /*     0     6 */

	/* size: 6, cachelines: 1, members: 1 */
	/* last cacheline: 6 bytes */
};

struct sta_inactive_t {
	u8                         mac[6];               /*     0     6 */

	/* size: 6, cachelines: 1, members: 1 */
	/* last cacheline: 6 bytes */
};

Signed-off-by: Mihaela Muraru <mihaela.muraru21@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>