dt-bindings: PCI: qcom,pcie-sm8550: Add SM8750 compatible

dt-bindings: PCI: qcom,pcie-sm8550: Add SM8750 compatible

PCIe controller present in SM8750 SoC is backwards compatible with the
controller present in SM8550 SoC. Hence, add the compatible with SM8550
fallback.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250826-pakala-v3-1-721627bd5bb0@oss.qualcomm.com