iio: pressure: bmp280: Fix uninitialized variable

clang found that the "offset" in bmp580_trigger_handler doesn't get
initialized before access. Add proper initialization to this variable.

Signed-off-by: Yo-Jung Lin (Leo) <0xff07@gmail.com>
Link: https://patch.msgid.link/20241011115334.367736-1-0xff07@gmail.com


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