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 err_put_buffers cleanup path of iio_hw_consumer_alloc(), the code was using list_for_each_entry() to iterate through buffers while calling iio_buffer_put() which can free the current buffer if refcount drops to 0. The list_for_each_entry() loop macro then evaluates buf->head.next to continue iteration, accessing the freed buffer. Fix this by using list_for_each_entry_safe().