iio: mlx90614: Drop MLX90614_CONST_EMISSIVITY_RESOLUTION

The MLX90614_CONST_EMISSIVITY_RESOLUTION can be calculated from
MLX90614_CONST_RAW_EMISSIVITY_MAX, perform the calculation inline
and drio the MLX90614_CONST_EMISSIVITY_RESOLUTION.

Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Crt Mori <cmo@melexis.com>
Link: https://lore.kernel.org/r/20230510102251.10118-4-marex@denx.de


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>