iio: pressure: bmp280: Rearrange vars in reverse xmas tree order

Small cleanup reordering local variable declarations following reverse
christmas tree convention.

Signed-off-by: Angel Iglesias <ang.iglesiasg@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/bb63a996eb9c4555bf83471770f0169d2627e79c.1697994521.git.ang.iglesiasg@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>