dt-bindings: PCI: cadence: Remove "mem" from reg binding

"mem" is not a memory resource and it overlaps with PCIe config space
and memory region. Remove "mem" from reg binding.

Link: https://lore.kernel.org/r/20200722110317.4744-8-kishon@ti.comSigned-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>

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

@@ -18,13 +18,12 @@ properties:
     const: cdns,cdns-pcie-host
 
   reg:
-    maxItems: 3
+    maxItems: 2
 
   reg-names:
     items:
       - const: reg
       - const: cfg
-      - const: mem
 
   msi-parent: true
 
@@ -49,9 +48,8 @@ examples:
             device-id = <0x0200>;
 
             reg = <0x0 0xfb000000  0x0 0x01000000>,
-                  <0x0 0x41000000  0x0 0x00001000>,
-                  <0x0 0x40000000  0x0 0x04000000>;
-            reg-names = "reg", "cfg", "mem";
+                  <0x0 0x41000000  0x0 0x00001000>;
+            reg-names = "reg", "cfg";
 
             ranges = <0x02000000 0x0 0x42000000  0x0 0x42000000  0x0 0x1000000>,
                      <0x01000000 0x0 0x43000000  0x0 0x43000000  0x0 0x0010000>;