dt-bindings: PCI: qcom,pcie-apq8084: Move APQ8084 to dedicated schema

dt-bindings: PCI: qcom,pcie-apq8084: Move APQ8084 to dedicated schema

Move APQ8084 PCIe devices from qcom,pcie.yaml binding to a dedicated
file to make reviewing and maintenance easier.

New schema is equivalent to the old one with few changes:
 - Adding a required compatible, which is actually redundant.
 - Drop the really obvious comments next to clock/reg/reset-names items.

After moving the qcom,pcie.yaml becames empty thus can be entirely
removed.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20251217-dt-bindings-pci-qcom-v2-12-873721599754@oss.qualcomm.com