Input: synaptics-rmi4 - add device tree support for RMI4 I2C devices

Add devicetree binding for I2C devices and add bindings for optional
parameters in the function drivers. Parameters for function drivers are
defined in child nodes for each of the functions.

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index 55df1d4..7a1bf68 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -220,6 +220,7 @@
 st	STMicroelectronics
 ste	ST-Ericsson
 stericsson	ST-Ericsson
+syna	Synaptics Inc.
 synology	Synology, Inc.
 tbs	TBS Technologies
 tcl	Toby Churchill Ltd.