dt-bindings: PCI: ti,am65: Fix remaining binding warnings

dt-bindings: PCI: ti,am65: Fix remaining binding warnings

This adds the missing num-viewport, phys and phy-name properties to the
schema. Based on driver code, num-viewport is required for the root
complex, phys are optional. Their number corresponds to the number of
lanes. The AM65x supports up to 2 lanes.

Link: https://lore.kernel.org/linux-pci/8032b018-c870-403a-9dd9-63440de1da07@siemens.com
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>