iio: adc: ti-ads1298: Remove unnecessary CONFIG2 write during init

iio: adc: ti-ads1298: Remove unnecessary CONFIG2 write during init

The driver was enabling the internal test signal (INT_TEST), double
amplitude (TEST_AMP), and fast frequency (TEST_FREQ_FAST) bits in
CONFIG2 during initialization. These bits activate an internal square
wave generator intended for device testing and calibration, not normal
ECG operation.

CONFIG2 defaults to having only the RESERVED bit set after reset, which
is the correct value for normal operation. Remove the write entirely
since it would just be writing the reset default value.

Suggested-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Md Shofiqul Islam <shofiqtest@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>