drm/panel: simple: Remove useless drm_mode_set_name()

drm_display_mode_from_videomode() already calls drm_mode_set_name() on
the provided mode.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
[treding@nvidia.com: slightly reword commit message]
Signed-off-by: Thierry Reding <treding@nvidia.com>