iio: freq: admv1014: Fix warning about dubious x & !y and improve readability

iio: freq: admv1014: Fix warning about dubious x & !y and improve readability

The warning comes from __BF_FIELD_CHECK()
specifically

BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?		\
		 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
		 _pfx "value too large for the field"); \

The code was using !(enum value) which is not particularly easy to follow
so replace that with explicit matching and use of ? 0 : 1; or ? 1 : 0;
to improve readability.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Link: https://lore.kernel.org/r/20220511090006.90502-1-antoniu.miclaus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>