drivers: iio: max1027: Fix sparse warning: "dubious: x | !y"

Fixing below warning:
drivers/iio/adc/max1027.c:241:34: warning: dubious: x | !y .

Signed-off-by: Sandhya Bankar <bankarsandhya512@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>