dt-bindings: touchscreen: ti,am3359-tsc: Remove deprecated text file

Now that the three hardware peaces described in this file have been
translated in yaml in 3 dedicated files (MFD, touchscreen controller and
ADC) it is time to remove this text file.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211015081506.933180-6-miquel.raynal@bootlin.com