ethernet: s2io: Use ether_addr_to_u64() to convert ethernet address

Use ether_addr_to_u64() to convert an Ethernet address into a u64 value,
instead of directly calculating, as this is exactly what
this function does.

Signed-off-by: Li Zetao <lizetao1@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230808113849.4033657-1-lizetao1@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>