ARM: dt: tegra20: add pinmux to device tree

This adds a complete pinmux configuration to all Tegra20 device tree
files. This allows removal of board-dt-tegra20.c's use of the pinmux
board files, and the special device tree handling in board-pinmux.c.

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