usb: phy: snps: Pass param override reg values from device tree

Pass value, register offset pair from device tree for phy param
override registers X0, X1, X2 and X3. Values need to be programmed
during phy init sequence.

Change-Id: I611810b9fe9a1586ae1db0ca451a4491aa832f56
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>