octeontx2-af: Use u64_to_ether_addr() to convert ethernet address

octeontx2-af: Use u64_to_ether_addr() to convert ethernet address

Use u64_to_ether_addr() to convert a u64 value to an Ethernet MAC address,
instead of directly calculating, as this is exactly what this
function does.

Signed-off-by: Li Zetao <lizetao1@huawei.com>
Acked-by: Geethasowjanya Akula <gakula@marvell.com>
Link: https://lore.kernel.org/r/20230808114504.4036008-3-lizetao1@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>