staging: ks7010: refactor ks_wlan_set_wap function

Make use of ether_addr_copy instead of memcpy for copying
ethernet address data in ks_wlan_set_wap function and avoid
an 'else' just changing if logic to check invalid values first.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>