dt-bindings: ata: dwc-ahci: add PHY clocks

Add PHY transmit and receive clocks as described by the
DW SATA AHCI HW manual.

Suggested-by: Serge Semin <[e-mail]>
Reviewed-by: Serge Semin <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>
Signed-off-by: Damien Le Moal <[e-mail]>

Documentation/devicetree/bindings/ata/snps,dwc-ahci-common.yaml

···
       PM-alive clock, RxOOB detection clock, embedded PHYs reference (Rx/Tx)
       clock, etc.
     minItems: 1
-    maxItems: 4
+    maxItems: 6
 
   clock-names:
     minItems: 1
-    maxItems: 4
+    maxItems: 6
     items:
       oneOf:
         - description: Application APB/AHB/AXI BIU clock
···
           const: pmalive
         - description: RxOOB detection clock
           const: rxoob
+        - description: PHY Transmit Clock
+          const: asic
+        - description: PHY Receive Clock
+          const: rbc
         - description: SATA Ports reference clock
           const: ref