ice: add basic devlink subfunctions support

Implement devlink port handlers responsible for ethernet type devlink
subfunctions. Create subfunction devlink port and setup all resources
needed for a subfunction netdev to operate. Configure new VSI for each
new subfunction, initialize and configure interrupts and Tx/Rx resources.
Set correct MAC filters and create new netdev.

For now, subfunction is limited to only one Tx/Rx queue pair.

Only allocate new subfunction VSI with devlink port new command.
Allocate and free subfunction MSIX interrupt vectors using new API
calls with pci_msix_alloc_irq_at and pci_msix_free_irq.

Support both automatic and manual subfunction numbers. If no subfunction
number is provided, use xa_alloc to pick a number automatically. This
will find the first free index and use that as the number. This reduces
burden on users in the simple case where a specific number is not
required. It may also be slightly faster to check that a number exists
since xarray lookup should be faster than a linear scan of the dyn_ports
xarray.

Co-developed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Piotr Raczynski <piotr.raczynski@intel.com>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>