xhci: Recognize USB 3.0 devices as superspeed at powerup

On Intel Panther Point chipset USB 3.0 devices show up as
high-speed devices on powerup, but after an s3 cycle they are
correctly recognized as SuperSpeed. At powerup switch the port
to xHCI so that USB 3.0 devices are correctly recognized.

BugLink: http://bugs.launchpad.net/bugs/1000424



This patch should be backported to kernels as old as 3.0, that contain
commit ID 69e848c2 "Intel xhci: Support
EHCI/xHCI port switching."

Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org