common/sfc_efx/base: add multi-host function mport selector

common/sfc_efx/base: add multi-host function mport selector

Provide helper function to compose multi-host aware PCIe
function M-port selector.

The firmware expects mport selectors to use different sets of values to
represent a PCIe interface in mport selectors and elsewhere. In order to
avoid having the user perform the conversion themselves, it is now done
automatically when a selector is constructed.

In addition, a type has been added to libefx for possible PCIe
interfaces.
This is done to abstract different representations away from the users.

Allow to support matching traffic coming from an arbitrary PCIe
end-point of the NIC and redirect traffic to it.

Signed-off-by: Viacheslav Galaktionov <viacheslav.galaktionov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>