iio: adc: meson: simplify MESON_SAR_ADC_REG11 register access

iio: adc: meson: simplify MESON_SAR_ADC_REG11 register access

Simply check the max_register value to decide whether
MESON_SAR_ADC_REG11 is present on the current IP revision. This allows
dropping two additional bool fields from struct meson_sar_adc_param
which previously had to be manually kept in sync. No functional changes
intended.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://patch.msgid.link/20241224142941.97759-4-martin.blumenstingl@googlemail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>