dt-bindings: clock: ti: Convert gate.txt to json-schema

dt-bindings: clock: ti: Convert gate.txt to json-schema

Convert the OMAP gate clock device tree binding to json-schema.
Specify the creator of the original binding as a maintainer.
Choose GPL-only license because original binding was also GPL.
Clean up the examples during conversion to meet modern standards and
remove examples with no additional value.
Due to usage in code and existing devicetree binding, add the
ti,set-rate-parent property.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Link: https://lore.kernel.org/r/20250105170854.408875-2-andreas@kemnade.info
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>