net: Add SIOCGI2CPB ioctl & add page/bank fields to ifi2creq

This commit adds page & bank fields to ifi2creq in preparation
for adding CMIS support for 400g optics to ifconfig.
The new ioctl SIOCGI2CPB is added, so that drivers can distinguish
between callers asking for page/bank selection and legacy callers
that simply failed to zero out all ifi2creq fields.

The mlx5en(4) driver and iflib(4) driver frameork have been updated
to use this new SIOCGI2CPB ioctl and support page/bank operations.
A follow-on patchset will add support to ifconfig for reporting
data from CMIS optics.

This has been tested on Nvidia ConnectX-7 and Broadcom Thor2 (using
out of tree driver) based NICs.

Differential Revision: https://reviews.freebsd.org/D55912
Sponsored by: Netflix Inc.
Reviewed by: kib