iio: accel: mma8452: Rename config structs for readability

Rename structs holding event configuration registers
to more appropriate names. This naming is consistent
with the event config register names given in the
mma845x and fxls8471 datasheets.

Signed-off-by: Harinath Nampally <harinath922@gmail.com>
Acked-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>