dt-bindings: sdhci-omap: Add bindings for the sdhci-omap controller

Add binding for the TI's sdhci-omap controller.
Signed-off-by: NKishon Vijay Abraham I <kishon@ti.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/sdhci-omap.txt

+* TI OMAP SDHCI Controller
+
+Refer to mmc.txt for standard MMC bindings.
+
+Required properties:
+- compatible: Should be "ti,dra7-sdhci" for DRA7 and DRA72 controllers
+- ti,hwmods: Must be "mmc<n>", <n> is controller instance starting 1
+
+Example:
+	mmc1: mmc@4809c000 {
+		compatible = "ti,dra7-sdhci";
+		reg = <0x4809c000 0x400>;
+		ti,hwmods = "mmc1";
+		bus-width = <4>;
+		vmmc-supply = <&vmmc>; /* phandle to regulator node */
+	};