phy: zynqmp: Add serdes/psgtr driver

Add PSGTR driver for Xilinx ZynqMP.
The most of configurations are taken from Linux kernel psgtr driver.

USB3.0 and SGMII configurations are tested on SOM. In SGMII case also
IOU_SLCR reg is updated to get proper clock setup and signal detection
configuration.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/36e6e9d3baf8511af1916e91e4887032ca2b6c20.1641458978.git.michal.simek@xilinx.com