ARM: tegra: colibri-eval: Add comment concerning SD/MMC

Instead of adding an otherwise unused sdmmc label just add a comment.
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra30-colibri-eval-v3.dts

@@ -84,6 +84,7 @@ spidev0: spi@1 {
 		};
 	};
 
+	/* SD/MMC */
 	sdhci@78000200 {
 		status = "okay";
 		bus-width = <4>;