dt-bindings: mmc: tegra: Add pinctrl for SDMMC drive strengths

Add pinctrls for 3V3 and 1V8 pad drive strength configuration for
Tegra210 sdmmc.

Tegra210 sdmmc has pad configuration registers in pinmux register
domain and handled thru pinctrl to pinmux device node.

Tegra186 and Tegra194 has pad configuration register with in the
SDMMC register domain itself and are handles thru drive strength
properties in sdmmc device node.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -39,12 +39,16 @@ sdhci@c8000200 {
 	bus-width = <8>;
 };
 
-Optional properties for Tegra210 and Tegra186:
+Optional properties for Tegra210, Tegra186 and Tegra194:
 - pinctrl-names, pinctrl-0, pinctrl-1 : Specify pad voltage
   configurations. Valid pinctrl-names are "sdmmc-3v3" and "sdmmc-1v8"
   for controllers supporting multiple voltage levels. The order of names
   should correspond to the pin configuration states in pinctrl-0 and
   pinctrl-1.
+- pinctrl-names : "sdmmc-3v3-drv" and "sdmmc-1v8-drv" are applicable for
+  Tegra210 where pad config registers are in the pinmux register domain
+  for pull-up-strength and pull-down-strength values configuration when
+  using pads at 3V3 and 1V8 levels.
 - nvidia,only-1-8-v : The presence of this property indicates that the
   controller operates at a 1.8 V fixed I/O voltage.
 - nvidia,pad-autocal-pull-up-offset-3v3,