phy: amlogic: Add Amlogic AXG PCIE PHY Driver

This adds support for the PCI PHY found in the Amlogic AXG SoC Family.
This will allow to mutualize code in pci-meson.c between AXG and G12A
SoC.

This PHY also uses and chains an analog PHY, which on AXG platform
is needed to have reliable PCIe communication.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>