mfd: ti_am335x_tscadc: Support the correctly spelled DT property

There was in the past a typo in the coordinate readouts property. The
bindings have been updated, the touchscreen driver as well and now
supports both. However, the MFD driver that is in charge of verifying
the validity of the property only checks the bogus one. Add support for
the correctly spelled DT property.

Fixes: c9aeb249 ("Input: ti_am335x_tsc - fix spelling mistake in TSC/ADC DT binding")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211015081506.933180-38-miquel.raynal@bootlin.com