iio: pressure: bmp280: Use sizeof() for denominator

Instead of using magic number 2 as a denominator, make it intuitive by
using sizeof().

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20241202181907.21471-3-vassilisamir@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>