dt-bindings: serial: fsl-lpuart: add i.MXRT1170 compatible

Add i.MXRT1170 compatible string to Documentation.

Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221107071511.2764628-5-Mr.Bossman075@gmail.com


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