dt-bindings: mmc: tegra: Reformat compatible string list

The list of compatible strings is somewhat difficult to read and extend.
Reformat it into a list to make it more easily extensible.

While at it, also remove the "plus one of the above" clause because it
isn't actually valid.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/nvidia,tegra20-sdhci.txt

@@ -7,11 +7,12 @@ This file documents differences between the core properties described
 by mmc.txt and the properties used by the sdhci-tegra driver.
 
 Required properties:
-- compatible : For Tegra20, must contain "nvidia,tegra20-sdhci".
-  For Tegra30, must contain "nvidia,tegra30-sdhci".  For Tegra114,
-  must contain "nvidia,tegra114-sdhci".  For Tegra124, must contain
-  "nvidia,tegra124-sdhci".  Otherwise, must contain "nvidia,<chip>-sdhci",
-  plus one of the above, where <chip> is tegra132 or tegra210.
+- compatible : should be one of:
+  - "nvidia,tegra20-sdhci": for Tegra20
+  - "nvidia,tegra30-sdhci": for Tegra30
+  - "nvidia,tegra114-sdhci": for Tegra114
+  - "nvidia,tegra124-sdhci": for Tegra124 and Tegra132
+  - "nvidia,tegra210-sdhci": for Tegra210
 - clocks : Must contain one entry, for the module clock.
   See ../clocks/clock-bindings.txt for details.
 - resets : Must contain an entry for each entry in reset-names.