dt-bindings: ata: atmel: remove at91 compact flash documentation

The compatible "at91rm9200-cf" is not used by any driver, hence remove the
corresponding documentation.
Signed-off-by: Hari Prasath Gujulan Elango <Hari.PrasathGE@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
[cassel: add missing space in commit log]
Signed-off-by: Niklas Cassel <cassel@kernel.org>

Documentation/devicetree/bindings/ata/atmel-at91_cf.txt

-Atmel AT91RM9200 CompactFlash
-
-Required properties:
-- compatible : "atmel,at91rm9200-cf".
-- reg : should specify localbus address and size used.
-- gpios : specifies the gpio pins to control the CF device. Detect
-  and reset gpio's are mandatory while irq and vcc gpio's are
-  optional and may be set to 0 if not present.
-
-Example:
-compact-flash@50000000 {
-	compatible = "atmel,at91rm9200-cf";
-	reg = <0x50000000 0x30000000>;
-	gpios = <&pioC 13 0	/* irq */
-		 &pioC 15 0 	/* detect */
-		 0		/* vcc */
-		 &pioC  5 0	/* reset */
-		>;
-};