dt-bindings: timer: gpt: Add i.MXRT compatible Documentation

Both the i.MXRT1170 and 1050 have the same GPT timer as "fsl,imx6dl-gpt"
Add i.MXRT to the compatible list.

Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20221107071511.2764628-4-Mr.Bossman075@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>