pinctrl: tegra: Add complete device tree support

Implement pinctrl_ops dt_node_to_map() and dt_free_map(). These allow
complete specification of the desired pinmux configuration using device
tree.

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