dt-bindings: ata: Document BCM7216 AHCI controller compatible

The BCM7216 AHCI controller makes use of a specific reset controller
line/name, document the compatible string and the optional reset
properties.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/devicetree/bindings/ata/brcm,sata-brcm.txt

@@ -5,6 +5,7 @@ Each SATA controller should have its own node.
 
 Required properties:
 - compatible         : should be one or more of
+			"brcm,bcm7216-ahci"
 			"brcm,bcm7425-ahci"
 			"brcm,bcm7445-ahci"
 			"brcm,bcm-nsp-ahci"
@@ -14,6 +15,12 @@ Required properties:
 - reg-names          : "ahci" and "top-ctrl"
 - interrupts         : interrupt mapping for SATA IRQ
 
+Optional properties:
+
+- reset: for "brcm,bcm7216-ahci" must be a valid reset phandle
+  pointing to the RESCAL reset controller provider node.
+- reset-names: for "brcm,bcm7216-ahci", must be "rescal".
+
 Also see ahci-platform.txt.
 
 Example: