drm/sti/sti_tvout: Provide a bunch of missing function names

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/sti/sti_tvout.c:166: warning: expecting prototype for Set the clipping mode of a VIP(). Prototype was for tvout_vip_set_color_order() instead
 drivers/gpu/drm/sti/sti_tvout.c:187: warning: expecting prototype for Set the clipping mode of a VIP(). Prototype was for tvout_vip_set_clip_mode() instead
 drivers/gpu/drm/sti/sti_tvout.c:203: warning: expecting prototype for Set the rounded value of a VIP(). Prototype was for tvout_vip_set_rnd() instead
 drivers/gpu/drm/sti/sti_tvout.c:223: warning: expecting prototype for Select the VIP input(). Prototype was for tvout_vip_set_sel_input() instead
 drivers/gpu/drm/sti/sti_tvout.c:258: warning: expecting prototype for Select the input video signed or unsigned(). Prototype was for tvout_vip_set_in_vid_fmt() instead
 drivers/gpu/drm/sti/sti_tvout.c:274: warning: expecting prototype for Set preformatter matrix(). Prototype was for tvout_preformatter_set_matrix() instead
 drivers/gpu/drm/sti/sti_tvout.c:299: warning: expecting prototype for Start VIP block for DVO output(). Prototype was for tvout_dvo_start() instead
 drivers/gpu/drm/sti/sti_tvout.c:353: warning: expecting prototype for Start VIP block for HDMI output(). Prototype was for tvout_hdmi_start() instead
 drivers/gpu/drm/sti/sti_tvout.c:402: warning: expecting prototype for Start HDF VIP and HD DAC(). Prototype was for tvout_hda_start() instead

Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210602143300.2330146-8-lee.jones@linaro.org