dt-bindings: fxas21002c: convert bindings to yaml

Convert fxas21002c gyroscope sensor bindings documentation to
yaml schema, remove the textual bindings document and update MAINTAINERS entry.

Signed-off-by: Rui Miguel Silva <rmfrfs@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201014104926.688666-1-rmfrfs@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>