xhci: Add Etron XHCI_TRUST_TX_LENGTH quirk.

Gary reports that with recent kernels, he notices more xHCI driver
warnings:

xhci_hcd 0000:03:00.0: WARN Successful completion on short TX: needs XHCI_TRUST_TX_LENGTH quirk?

We think his Etron xHCI host controller may have the same buggy behavior
as the Fresco Logic xHCI host.  When a short transfer is received, the
host will mark the transfer as successfully completed when it should be
marking it with a short completion.

Fix this by turning on the XHCI_TRUST_TX_LENGTH quirk when the Etron
host is discovered.  Note that Gary has revision 1, but if Etron fixes
this bug in future revisions, the quirk will have no effect.

This patch should be backported to kernels as old as 2.6.36, that
contain a backported version of commit
1530bbc6 "xhci: Add new short TX quirk
for Fresco Logic host."

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: Gary E. Miller <gem@rellim.com>
Cc: stable@vger.kernel.org