test/dm: reset: Add reset_get_by_index[_nodev] test

Add sample dm reset test for reset_get_by_index and
reset_get_by_index_nodev functionality code.

Cc: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Simon Glass <sjg@chromium.org>