dt-bindings: pinctrl: Drop k3

dt-bindings: pinctrl: Drop k3

For convenience (less code duplication), the pin controller pin
configuration register values were defined in the bindings header.
These are not some IDs or other abstraction layer but raw numbers used
in the registers.

These constants do not fit the purpose of bindings. They do not
provide any abstraction, any hardware and driver independent ID. In
fact, the Linux pinctrl-single driver actually do not use the bindings
header at all.

Commit f2de003e1426 ("dt-bindings: pinctrl: k3: Deprecate header with
register constants") already moved users to the local header, so, drop
the binding header. See background discussion in [1].

While at it, clean up the MAINTAINERS file which is the only reference
left.

[1]: https://lore.kernel.org/linux-arm-kernel/71c7feff-4189-f12f-7353-bce41a61119d@linaro.org/

Suggested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230601173831.982429-1-nm@ti.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>