usb: phy: qusb: Set clamp_dig_n signal based on usb status

usb: phy: qusb: Set clamp_dig_n signal based on usb status

Analog and digital power rails connected to the phy can be turned
on/off in any order. This may result in random leakage in the phy
as it expects certain power rails to be on/off in certain order.
Avoid random leakage on qusb2 phy by
1. Disable pll when phy is suspended/disconnected.
2. Reset and assert clamp dig_n signal to put dp/dm lines in high
   impedance state.

Change-Id: I1bafa7f824af8bbb3f67a71b81bf23b0a9c7164e
Signed-off-by: Vamsi Krishna Samavedam <vskrishn@codeaurora.org>