dt-bindings: pinctrl: tegra194: Separate instances

Tegra194 has two separate instances of the pin controller, one called
AON (in the always-on domain) and another called "main". Instead of
treating them as a single pin controller, split them up into two
separate controllers. Doing so allows the mapping between the pinmux and
GPIO controllers to be trivial identity mappings and more cleanly
separates the AON from the main IP blocks.

Note that while this changes the DT node in an incompatible way, this
doesn't have any practical implications for backwards-compatibility. The
reason for this is that device trees have only reconfigured a very
narrow subset of pins of the main controller, so the new driver will
remain backwards-compatible with old device trees.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>