ARM: tegra: apalis: Add comment concerning eMMC

Instead of adding an otherwise unused emmc label just add a comment
describing what the SDHCI is routed to.
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra30-apalis.dtsi

@@ -636,6 +636,7 @@ pmc@7000e400 {
 		nvidia,sys-clock-req-active-high;
 	};
 
+	/* eMMC */
 	sdhci@78000600 {
 		status = "okay";
 		bus-width = <8>;