staging: greybus: codecs: use dedicated list iterator variable

staging: greybus: codecs: use dedicated list iterator variable

In preparation to limit the scope of the list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Reviewed-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220321123712.3068778-1-jakobkoschel@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>