xhci: clean up event ring checks from inc_enq()

	chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;

	/* If this is not event ring, there is one less usable TRB */

	if (ring->type != TYPE_EVENT &&

			!last_trb(xhci, ring, ring->enq_seg, ring->enqueue))

	if (!last_trb(xhci, ring, ring->enq_seg, ring->enqueue))

		ring->num_trbs_free--;

	next = ++(ring->enqueue);

	ring->enq_updates++;

	/* Update the dequeue pointer further if that was a link TRB or we're at

	 * the end of an event ring segment (which doesn't have link TRBS)

	 */

	/* Update the dequeue pointer further if that was a link TRB */

	while (last_trb(xhci, ring, ring->enq_seg, next)) {

		if (ring->type != TYPE_EVENT) {

		/*

			 * If the caller doesn't plan on enqueueing more

			 * TDs before ringing the doorbell, then we

			 * don't want to give the link TRB to the

			 * hardware just yet.  We'll give the link TRB

			 * back in prepare_ring() just before we enqueue

			 * the TD at the top of the ring.

		 * If the caller doesn't plan on enqueueing more TDs before

		 * ringing the doorbell, then we don't want to give the link TRB

		 * to the hardware just yet. We'll give the link TRB back in

		 * prepare_ring() just before we enqueue the TD at the top of

		 * the ring.

		 */

		if (!chain && !more_trbs_coming)

			break;

			/* If we're not dealing with 0.95 hardware or

			 * isoc rings on AMD 0.96 host,

			 * carry over the chain bit of the previous TRB

		/* If we're not dealing with 0.95 hardware or isoc rings on

		 * AMD 0.96 host, carry over the chain bit of the previous TRB

		 * (which may mean the chain bit is cleared).

		 */

		if (!(ring->type == TYPE_ISOC &&

					(xhci->quirks & XHCI_AMD_0x96_HOST))

						&& !xhci_link_trb_quirk(xhci)) {

				next->link.control &=

					cpu_to_le32(~TRB_CHAIN);

				next->link.control |=

					cpu_to_le32(chain);

		      (xhci->quirks & XHCI_AMD_0x96_HOST)) &&

		    !xhci_link_trb_quirk(xhci)) {

			next->link.control &= cpu_to_le32(~TRB_CHAIN);

			next->link.control |= cpu_to_le32(chain);

		}

		/* Give this link TRB to the hardware */

		wmb();

		next->link.control ^= cpu_to_le32(TRB_CYCLE);

		/* Toggle the cycle bit after the last ring segment. */

			if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {

		if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next))

			ring->cycle_state ^= 1;

			}

		}

		ring->enq_seg = ring->enq_seg->next;

		ring->enqueue = ring->enq_seg->trbs;

		next = ring->enqueue;