ARM: dt: tegra cardhu: fix typo in SDHCI node name

Cardhu's eMMC controller is on sdhci@78000600, not sdhci@78000400.
Fix the typo. This roughly doubles the IO performance, since the
support-8bit property actually takes effect.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Cc: stable@kernel.org # v3.4