dt-bindings: mfd: ti,am3359-tscadc: Describe am4372 MFD compatible

A more recent version of the am3359 ADC/Touchscreen controller is
available on certain SoCs of the am437x family. This IP has evolved a
little bit and deserves its own compatible.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211015081506.933180-7-miquel.raynal@bootlin.com