iio: chemical: bme680: cleanup bme680_read_calib formatting

Use the full 80 char width to reduce the number of lines taken
by function calls.

Remove blank lines where it aids clarity by bringing together related
code blocks (such as read hi and low bytes and then combine them into
one value).

Signed-off-by: David Frey <dpfrey@gmail.com>
Reviewed-by: Himanshu Jha <himanshujha199640@gmail.com>
Tested-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>