mmc: tegra: use correct alias for SDHCI/MMC nodes

The Tegra MMC driver currently honors "sdhci" entries in /aliases. The
MMC core however uses "mmc" entries in /aliases. This difference will be
relevant once the Tegra MMC driver is converted to DM, and the MMC core
handles alias lookups. To avoid issues during that conversion, fix the
Tegra MMC driver and all Tegra DTs to use the same alias name as the MMC
core does.

Cc: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>