elan: fix frame leak in elan_submit_image
Fix losing head of
elandev->frames when skipping last captured frame(s). Use a separate list pointer for the frames we want to process. Leave
elandev->frames intact and let
elan_dev_reset handle cleanup.
PS: examples/* no longer work with elan unless I comment out https://gitlab.freedesktop.org/libfprint/libfprint/blob/master/libfprint/fpi-poll.c#L170