staging: rtl8188eu: refactor rtw_macaddr_cfg()

Use ether_addr_copy() instead of memcpy() to copy the mac address.

Using is_broadcast_ether_addr() and is_zero_ether_addr() instead of
testing each byte of the mac[] array for 0xff and 0x00 shortens the
code and improves readability.

Instead of a fixed default mac address use a random one to reduce the
likelihood of mac address collision.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>