dt-bindings: iio: adc: Remove the property "aspeed,trim-data-valid"

If the property is set on a device without valid trimming data in the OTP
the ADC will not function correctly. Therefore, this patch drops the use
of this property to avoid this scenario.

Fixes: 2bdb2f00

 ("dt-bindings: iio: adc: Add ast2600-adc bindings")
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221114025057.10843-2-billy_tsai@aspeedtech.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>