ice: avoid XDP checks in ice_clean_tx_irq()

Commit 9610bd98 ("ice: optimize XDP_TX workloads") introduced Tx IRQ
cleaning routine dedicated for XDP rings. Currently it is impossible to
call ice_clean_tx_irq() against XDP ring, so it is safe to drop
ice_ring_is_xdp() calls in there.

Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>  (A Contingent Worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>