phy: usb: Add "wake on" functionality for newer Synopsis XHCI controllers

Add "wake on" support for the newer Synopsis based XHCI only controller.
This works on the 72165 and 72164 and newer chips and does not work
on 7216 based systems. Also switch the USB sysclk to a slower clock
on suspend to save additional power in S2. The clock switch will only
save power on the 72165b0 and newer chips and is a nop on older chips.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220215032422.5179-1-f.fainelli@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>