dt-bindings: PCI: ti,j721e-pci-*: Add j784s4-pci-* compatible strings

Add definition for j784s4-pci-ep and j784s4-pci-host devices along with
schema checks for num-lanes.

Link: https://lore.kernel.org/linux-pci/20231128054402.2155183-3-s-vadapalli@ti.com


Signed-off-by: Matt Ranostay <mranostay@ti.com>
Signed-off-by: Achal Verma <a-verma1@ti.com>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>