dt-bindings: gpio: Convert Unisoc EIC controller binding to yaml

Convert the Unisoc EIC controller binding to DT schema format.
Update the maxItems of 'reg' property, since the current gpio-eic-sprd
driver supports 3 reg items. Also removed a few similar examples.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>