ice: allow 3k MTU for XDP

At this point ice driver is able to work on order 1 pages that are split
onto two 3k buffers. Let's reflect that when user is setting new MTU
size and XDP is present on interface.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>