pinctrl: tegra: move pinconf-tegra.h content into drivers/pinctrl

Now that Tegra's pinmux is configured solely from device tree, there's
no need for the pinconf types to be defined in arch/arm/mach-tegra/.
Move it into the pinctrl directory to clean up mach-tegra, as a pre-
requisite for single-zImage.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>