xilinx_emacps.c: Fix three random MAC address assignment issues

When a random address has been assigned to the controller, the entry
addr_assign_type in sysfs still claims the address has been assigned
by other means. Fix this by replacing "random_ether_addr" by
"eth_hw_addr_random", which also sets the NET_ADDR_RANDOM value.

Use the more efficient "ether_addr_copy" instead of memcpy(), because
the addr variable is u16 aligned.

Fix the incorrect message "invalid address, use assigned" which is the
very opposite of what is going to happen. Log "invalid address, use random"
instead.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Acked-by: Punnaiah Choudary Kalluri <punnaia@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>