pinctrl/lantiq: updating devicetree binding description

This patch adds the new dedicated "lantiq,<chip>-pinctrl" compatible strings
to the devicetree bindings Documentation, where <chip> is one of "ase",
"danube", "xrx100", "xrx200" or "xrx300" and marks the "lantiq,pinctrl-xway",
"lantiq,pinctrl-ase" and "lantiq,pinctrl-xr9" compatible strings as DEPRECATED.

Signed-off-by: Martin Schiller <mschiller@tdt.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>