ath10k: use ether_addr_copy()

As suggeested by checkpatch:

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

In wmi.c I had to change due to sparse warnings copying of struct wmi_mac_addr
from form &cmd->peer_macaddr.addr to cmd->peer_macaddr.addr. In
ath10k_wmi_set_ap_ps_param() I also added the missing ".addr" to the copy
command.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>