CVE-2026-63965: iio: pressure: bmp280: fix stack leak in bmp580 trigger handler

In the Linux kernel, the following vulnerability has been resolved:

iio: pressure: bmp280: fix stack leak in bmp580 trigger handler

bmp580triggerhandler() declares its scan buffer on the stack without an initializer and then memcpy()s 3 bytes of 24-bit sensor data into each 4-byte le32 field. The high byte of comptemp and comppress is left uninitialized, and the channel storagebits is 32, so two bytes of stack are pushed to userspace per scan.

This is a regression from when the buffer lived in the private data, the move to a stack-local struct dropped the implicit zeroing. bme280triggerhandler() was fixed up to handle this bug, but this driver was not fixed because there was no padding hole, but rather a short-fill issue.

Fix this all by just zero-initializing the structure on the stack.