dt-bindings: sdhci-omap: Add K2G specific binding

Add binding for the TI's sdhci-omap controller present in K2G.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -4,7 +4,9 @@ Refer to mmc.txt for standard MMC bindings.
 
 Required properties:
 - compatible: Should be "ti,dra7-sdhci" for DRA7 and DRA72 controllers
+	      Should be "ti,k2g-sdhci" for K2G
 - ti,hwmods: Must be "mmc<n>", <n> is controller instance starting 1
+	     (Not required for K2G).
 
 Example:
 	mmc1: mmc@4809c000 {