USB: OTG: msm: Add support for power management

Implement runtime and system pm ops to put hardware into low power
mode (LPM). As part of LPM, USB clocks are turned off, PHY is put
into suspend state and PHY comparators are turned off if VBUS/Id
notifications are not required from PHY.

Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/otg/Kconfig

@@ -88,7 +88,8 @@ config USB_MSM_OTG_72K
 	help
 	  Enable this to support the USB OTG transceiver on MSM chips. It
 	  handles PHY initialization, clock management, and workarounds
-	  required after resetting the hardware. This driver is required
-	  even for peripheral only or host only mode configuration.
+	  required after resetting the hardware and power management.
+	  This driver is required even for peripheral only or host only
+	  mode configurations.
 
 endif # USB || OTG