ARM: tegra: pinmux: support Tegra210's e_io_hv pin option

Tegra210 has a per-pin option named e_io_hv, which indicates that the
pin's input path should be configured to be 3.3v-tolerant. Add support
for this.

Note that this is very similar to previous chip's rcv_sel option.
However, since the Tegra TRM names this option differently for the
different chips, we support the new name so that the code exactly matches
the naming in the TRM, to avoid confusion.

This patch incorporates a few fixes from Tom Warren <twarren@nvidia.com>.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>