drm/vc4: Correct generation check in vc4_hvs_lut_load

Commit 24c5ed3 ("drm/vc4: Introduce generation number enum")
incorrectly swapped a check of hvs->vc4->is_vc5 to
hvs->vc4->gen == VC4_GEN_4 in vc4_hvs_lut_load, hence breaking
loading the gamma look up table on Pi0-3.

Correct that conditional.

Fixes: 24c5ed3 ("drm/vc4: Introduce generation number enum")
Reported-by: Marek Szyprowski <[email protected]>
Closes: https://lore.kernel.org/dri-devel/[email protected]/
Tested-by: Marek Szyprowski <[email protected]>
Reviewed-by: Maíra Canal <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Dave Stevenson <[email protected]>

Author: 6by9

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -224,7 +224,7 @@ static void vc4_hvs_lut_load(struct vc4_hvs *hvs,
 	if (!drm_dev_enter(drm, &idx))
 		return;
 
-	if (hvs->vc4->gen == VC4_GEN_4)
+	if (hvs->vc4->gen != VC4_GEN_4)
 		goto exit;
 
 	/* The LUT memory is laid out with each HVS channel in order,