usb: dwc3-msm: Add sysfs node to enable SS host compliance

xHCI specs revision 1.1 mentions that if Compliance Transition
Capability (CTC) flag is set, then xHC supports software control
of the transition to Compliance mode. For this, we need to write
a value of 10 to Port Link State(PLS) field of PORTSC register
during dwc3_otg_start_host time after the xhci platform device
has been added. Then the link transitions to compliance state
on detection of first LFPS timeout.

Steps to enable compliance transition:
  1. Do not connect host cable
  2. echo y > /sys/devices/platform/a600000.ssusb/xhci_link_compliance
  3. Connect host cable with breakout fixture and start testing

Steps to disable compliance transition:
  1. Disconnect the host cable
  2. echo n > /sys/devices/platform/a600000.ssusb/xhci_link_compliance
  3. Connect host cable

Change-Id: I73225ccad105414d3ebd60f95138b9ecf65005d4
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>