ice: finish virtchnl.c split into rss.c

Move functions out of virt/virtchnl.c to virt/rss.c.

Same "git tricks" used as for the split into virt/queues.c
that is immediately preceding this split.

Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>