usb: phy: qusb: Update suspend/resume sequence for sdx20

Keep PLL in reset until we are fully ready to resume
ie. SE clock is enabled, and refgen current is stable, when
exiting XOSD. This prevents the attempt to lock PLL too early
and thereby possible failure to successfully resume.

Change-Id: I44cbf3222ce94494e7d45a8e645732a748fd1fa4
Signed-off-by: Devdutt Patnaik <dpatnaik@codeaurora.org>