dt-bindings: pinctrl: mediatek,mt6779-pinctrl: Add MT6797

Combine MT6797 pin controller document into MT6779 one. reg and
reg-names property constraints are set using conditionals.
A conditional is also used to make interrupt-related properties
required on the MT6779 pin controller only, since the MT6797
controller doesn't support interrupts (or not yet, at least).
drive-strength and slew-rate properties which weren't described
in the MT6779 document before are brought in from the MT6797 one.
Both pin controllers share a common driver core so they should
both support these properties.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221028153505.23741-5-y.oudjana@protonmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>