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

Documentation/devicetree/bindings/timer/fsl,imxgpt.yaml

@@ -31,6 +31,8 @@ properties:
           - enum:
               - fsl,imx6sl-gpt
               - fsl,imx6sx-gpt
+              - fsl,imxrt1050-gpt
+              - fsl,imxrt1170-gpt
           - const: fsl,imx6dl-gpt
 
   reg: