dt-bindings: PCI: microchip,pcie-host: fix missing clocks properties

Recent versions of dt-schema warn about unevaluatedProperties:
arch/riscv/boot/dts/microchip/mpfs-icicle-kit.dtb: pcie@2000000000: Unevaluated properties are not allowed ('clock-names', 'clocks', 'legacy-interrupt-controller', 'microchip,axi-m-atr0' were unexpected)
        From schema: Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml

The clocks are required to enable interfaces between the FPGA fabric
and the core complex, so add them to the binding.

Link: https://lore.kernel.org/r/20220819231415.3860210-3-mail@conchuod.ie
Fixes: 6ee6c89aac ("dt-bindings: PCI: microchip: Add Microchip PolarFire host binding")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml

@@ -25,6 +25,33 @@ properties:
       - const: cfg
       - const: apb
 
+  clocks:
+    description:
+      Fabric Interface Controllers, FICs, are the interface between the FPGA
+      fabric and the core complex on PolarFire SoC. The FICs require two clocks,
+      one from each side of the interface. The "FIC clocks" described by this
+      property are on the core complex side & communication through a FIC is not
+      possible unless it's corresponding clock is enabled. A clock must be
+      enabled for each of the interfaces the root port is connected through.
+      This could in theory be all 4 interfaces, one interface or any combination
+      in between.
+    minItems: 1
+    items:
+      - description: FIC0's clock
+      - description: FIC1's clock
+      - description: FIC2's clock
+      - description: FIC3's clock
+
+  clock-names:
+    description:
+      As any FIC connection combination is possible, the names should match the
+      order in the clocks property and take the form "ficN" where N is a number
+      0-3
+    minItems: 1
+    maxItems: 4
+    items:
+      pattern: '^fic[0-3]$'
+
   interrupts:
     minItems: 1
     items: