usb: phy: qmp: Put the QMP PHY in power down state on disconnect

Put the QMP PHY in power down state when cable is disconnected.
When cable is disconnected we don't need to put the PHY in
autonomous mode. Wake-up from XOSD is triggered from PMIC
interrupt. This provides additional power savings of 1mW.

Change-Id: I22f244186b113332ea8d17358f8b0cadd24ef150
Signed-off-by: Mayank Rana <mrana@codeaurora.org>