iio: sca3000: Fix a typo

All #define are about SCA3000_... except the last one.
Make it consistent.

s/SAC3000/SCA3000/

This #define is apparently unused up to now.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>