mmc: dt: Consolidate DT bindings

This patch unifies the current DT MMC bindings documentation and code,
adds generic MMC DT bindings documentation, and updates .dts files for
consistency.

[cjb: typo fixes, addition of max-frequency property]
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm/boot/dts/tegra-cardhu.dts b/arch/arm/boot/dts/tegra-cardhu.dts
index ac3fb75..67c6511 100644
--- a/arch/arm/boot/dts/tegra-cardhu.dts
+++ b/arch/arm/boot/dts/tegra-cardhu.dts
@@ -54,6 +54,7 @@
 		cd-gpios = <&gpio 69 0>; /* gpio PI5 */
 		wp-gpios = <&gpio 155 0>; /* gpio PT3 */
 		power-gpios = <&gpio 31 0>; /* gpio PD7 */
+		bus-width = <4>;
 	};
 
 	sdhci@78000200 {
@@ -66,5 +67,6 @@
 
 	sdhci@78000400 {
 		support-8bit;
+		bus-width = <8>;
 	};
 };