dt-bindings: gpio-vf610: add imx7ulp support

dt-bindings: gpio-vf610: add imx7ulp support

The Rapid General-Purpose Input and Output with 2 Ports (RGPIO2P)
on MX7ULP is similar to GPIO on Vibrid, except it has an extra
Port Data Direction Register (PDDR) used to configure the individual
port pins for input or output.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>