arm64: dts: imx8qxp-mek: Add i2c1 with pca9646

Add an initial description of the i2c1 bus with a pca9646 i2c switch and
various gpio expanders and sensors behind that. Only add the sensors
which already have upstream drivers.

According to the datasheet the pca9646 is software compatible with
pca9546 so no driver changes should be required.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>