GUSB2PHYCFG.ENBLSLPM enables the controller to assert low power signals
to the PHY. Unless disabled via device property, explicitly set
GUSB2PHYCFG.ENBLSLPM as it may not be set by default.
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>