CVE-2026-63930: iio: buffer: hw-consumer: fix use-after-free in error path

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

iio: buffer: hw-consumer: fix use-after-free in error path

In the errputbuffers cleanup path of iiohwconsumeralloc(), the code was using listforeachentry() to iterate through buffers while calling iiobufferput() which can free the current buffer if refcount drops to 0. The listforeachentry() loop macro then evaluates buf->head.next to continue iteration, accessing the freed buffer.

Fix this by using listforeachentrysafe().