mlxsw: pci: Obtain info about ports used by eXtended mezanine

The output of boardinfo command was extended to contain information
about XM. Indicates if is present and in case it is, tells which
localports are used for the connection. So parse this info and store it
in bus_info passed up to the driver.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>