Solve xHCI detect SS device as HS device issue.

Solve xHCI detect SS device as HS device issue.

BZ: 33811

This is a workaround for hardware bug. When USB3 phy in P3 state, its
RxDetect is not work well. So force PHY change to P2 state when USB3
controller want to perform receiver detection.

Change-Id: Ifbe3af1a47c784bd0afa4f5e0c20f5c228d6c161
Signed-off-by: Yu Wang <yu.y.wang@intel.com>
Reviewed-on: http://android.intel.com:8080/46561
Reviewed-by: Tang, Richard <richard.tang@intel.com>
Tested-by: Sun, Jianhua <jianhua.sun@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>