drm/vc4: crtc: Move the HVS gamma LUT setup to our init function

Since most of the HVS channel is setup in the init function, let's move the
gamma setup there too. As this makes the HVS mode_set function empty, let's
remove it in the process.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d439da8f1592a450a6ad35ab1f9e77def17c7965.1599120059.git-series.maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_txp.c

@@ -436,7 +436,6 @@ static const struct drm_crtc_helper_funcs vc4_txp_crtc_helper_funcs = {
 	.atomic_flush	= vc4_hvs_atomic_flush,
 	.atomic_enable	= vc4_txp_atomic_enable,
 	.atomic_disable	= vc4_txp_atomic_disable,
-	.mode_set_nofb	= vc4_hvs_mode_set_nofb,
 };
 
 static irqreturn_t vc4_txp_interrupt(int irq, void *data)