usb: host: xhci: update event ring dequeue pointer on purpose

On some situations, the software handles TRB events slower
than adding TRBs, then xhci_handle_event can't return zero
long time, the xHC will consider the event ring is full,
and trigger "Event Ring Full" error, but in fact, the software
has already finished lots of events, just no chance to
update ERDP (event ring dequeue pointer).

In this commit, we force update ERDP if half of TRBS_PER_SEGMENT
events have handled to avoid "Event Ring Full" error.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/1573836603-10871-2-git-send-email-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>