net: libwx: add base vf api for vf drivers

Implement mbox_write_and_read_ack functions which are
used to set basic functions like set_mac, get_link.etc
for vf.

Signed-off-by: Mengyuan Lou <mengyuanlou@net-swift.com>
Link: https://patch.msgid.link/20250704094923.652-3-mengyuanlou@net-swift.com


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