arm64: tegra: Use consistent SD/MMC aliases on Tegra234

arm64: tegra: Use consistent SD/MMC aliases on Tegra234

Tegra234 boards use a mixture of aliases for the SD/MMC hardware blocks,
which can lead to confusion. A common method was to use mmc3 as the
alias for the eMMC because "SDMMC3" happens to be the name of the
corresponding controller in the reference manual. This isn't a great
choice because there is no hardware named SDMMC0, so the mmc0 alias
would never get used with that nomenclature and in fact mmc1 and mmc2
wouldn't either in many configurations, thereby creating weird
discontiguous enumeration.

Instead of trying to match the aliases to the hardware block names, use
mmc0 to denote the device's primary SD/MMC controller (typically eMMC)
and mmc1 for the secondary SD/MMC controller (typically removable SD).
In cases where eMMC is the only controller we can omit the mmc1 alias
and if a device has no eMMC, the removable SD card can be aliased to
mmc0 instead.

Co-developed-by: Russell Xiao <russellx@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>