iio: pressure: bmp280: augment DT bindings

This adds standard device tree bindings for a reset GPIO line, and
the VDDD and VDDA power regulators.

Cc: devicetree@vger.kernel.org
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/pressure/bmp085.txt

-BMP085/BMP18x digital pressure sensors
+BMP085/BMP18x/BMP28x digital pressure sensors
 
 Required properties:
-- compatible: bosch,bmp085
+- compatible: must be one of:
+  "bosch,bmp085"
+  "bosch,bmp180"
+  "bosch,bmp280"
+  "bosch,bme280"
 
 Optional properties:
 - chip-id: configurable chip id for non-default chip revisions
@@ -10,6 +14,10 @@ Optional properties:
   value range is 0-3 with rising sensitivity.
 - interrupt-parent: should be the phandle for the interrupt controller
 - interrupts: interrupt mapping for IRQ
+- reset-gpios: a GPIO line handling reset of the sensor: as the line is
+  active low, it should be marked GPIO_ACTIVE_LOW (see gpio/gpio.txt)
+- vddd-supply: digital voltage regulator (see regulator/regulator.txt)
+- vdda-supply: analog voltage regulator (see regulator/regulator.txt)
 
 Example:
 
@@ -21,4 +29,7 @@ pressure@77 {
 	default-oversampling = <2>;
 	interrupt-parent = <&gpio0>;
 	interrupts = <25 IRQ_TYPE_EDGE_RISING>;
+	reset-gpios = <&gpio0 26 GPIO_ACTIVE_LOW>;
+	vddd-supply = <&foo>;
+	vdda-supply = <&bar>;
 };