Input: ads7846 - use spi_device_id table

As the driver supports more devices over time the single MODULE_ALIAS
is complete and raises several warnings:
SPI driver ads7846 has no spi_device_id for ti,tsc2046
SPI driver ads7846 has no spi_device_id for ti,ads7843
SPI driver ads7846 has no spi_device_id for ti,ads7845
SPI driver ads7846 has no spi_device_id for ti,ads7873

Fix this by adding a spi_device_id table and removing the manual
MODULE_ALIAS.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20240619122703.2081476-1-alexander.stein@ew.tq-group.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>