tegra2: Add more pinmux functions

This adds support for changing pinmux functions of pin groups. This is done
by defining a PMUX_FUNC_... enum which can be used to select the function for
each group using pinmux_set_func(). It is also possible to enable
pullup/pulldown, and the existing tristate functionality is retained.

Also provided is a means of configuring a list of pingroups by providing a
configuration table to pinmux_config_table().

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Warren <twarren@nvidia.com>