NFC: trf7970a: Document the 'irq-status-read-quirk' DT property

The mechanism for specifying that the trf7970a
being used by the driver has the "IRQ Status Read"
erratum has been changed to a device tree property
('irq-status-read-quirk').

Document the new device tree property.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

Documentation/devicetree/bindings/net/nfc/trf7970a.txt

@@ -14,6 +14,8 @@ Optional SoC Specific Properties:
 - pintctrl-0: Specifies the pin control groups used for this controller.
 - autosuspend-delay: Specify autosuspend delay in milliseconds.
 - vin-voltage-override: Specify voltage of VIN pin in microvolts.
+- irq-status-read-quirk: Specify that the trf7970a being used has the
+  "IRQ Status Read" erratum.
 
 Example (for ARM-based BeagleBone with TRF7970A on SPI1):
 
@@ -33,6 +35,7 @@ Example (for ARM-based BeagleBone with TRF7970A on SPI1):
 		vin-supply = <&ldo3_reg>;
 		vin-voltage-override = <5000000>;
 		autosuspend-delay = <30000>;
+		irq-status-read-quirk;
 		status = "okay";
 	};
 };