drm/vc4: hdmi: Correct interlaced timings again

The back porch timings were correct, only the sync offset was wrong.
Correct timing is now reported for 1080i and 576i, but the h offset is
incorrect for 480i for non-obvious reasons.

Fixes: fb10dc45 ("drm/vc4: hdmi: Correct HDMI timing registers for interlaced modes")
Signed-off-by: NDave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20221207-rpi-hvs-crtc-misc-v1-14-1f8e0770798b@cerno.techSigned-off-by: NMaxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -1307,11 +1307,12 @@ static void vc5_hdmi_set_timings(struct vc4_hdmi *vc4_hdmi,
 		     VC4_SET_FIELD(mode->crtc_vdisplay, VC5_HDMI_VERTA_VAL));
 	u32 vertb = (VC4_SET_FIELD(mode->htotal >> (2 - pixel_rep),
 				   VC5_HDMI_VERTB_VSPO) |
-		     VC4_SET_FIELD(mode->crtc_vtotal - mode->crtc_vsync_end,
+		     VC4_SET_FIELD(mode->crtc_vtotal - mode->crtc_vsync_end +
+				   interlaced,
 				   VC4_HDMI_VERTB_VBP));
 	u32 vertb_even = (VC4_SET_FIELD(0, VC5_HDMI_VERTB_VSPO) |
 			  VC4_SET_FIELD(mode->crtc_vtotal -
-					mode->crtc_vsync_end - interlaced,
+					mode->crtc_vsync_end,
 					VC4_HDMI_VERTB_VBP));
 	unsigned long flags;
 	unsigned char gcp;