dt-bindings: i2c: migrate mt7621 text bindings to YAML

dt-bindings: i2c: migrate mt7621 text bindings to YAML

SoC MT7621 I2C bindings used text format, so migrate them to YAML.
There are some additions to the binding that were not in the original
txt file. This binding is used in MT7621 and MT7628a Ralink SoCs. To
properly match both dts nodes in tree we need to add to the schema
'clocks', 'clock-names' and 'reset-names'. Both 'clock-names' and
'reset-names' use 'i2c' as string so maintain that as const in
the schema. Also, Properly update MAINTAINERS file to align the
changes.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220920052050.582321-1-sergio.paracuellos@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>