CVE-2026-98660: iio: pressure: bmp280: fix out-of-bounds access in sampling frequency lookup

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

iio: pressure: bmp280: fix out-of-bounds access in sampling frequency lookup

The sampling frequency tables store each frequency as an integer part and a fractional part in micro units. numsamplingfreqavail is initialized to the number of flattened integer elements because readavail() returns the table as a flat array.

bmp280writesamplingfrequency(), however, indexes the same table as a two-dimensional array and uses numsamplingfreqavail as the number of rows. Convert the flattened element count back to the number of rows before iterating over the table.