PCI: amlogic: Use AXG PCIE

Now that PCIE PHY has been introduced for AXG, the whole has_shared_phy
logic can be mutualized between AXG and G12A platforms.

This new PHY makes use of the shared MIPI/PCIE analog PHY found on AXG
platforms, which need to be used in order to have reliable PCIE
communications.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>