drm/vc4: Fix clock source for VEC PixelValve on BCM2711

On the BCM2711 (Raspberry Pi 4), the VEC is actually connected to
output 2 of pixelvalve3.

NOTE: This contradicts the Broadcom docs, but has been empirically
tested and confirmed by Raspberry Pi firmware devs.
Signed-off-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210520150344.273900-2-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -994,7 +994,7 @@ static const struct vc4_pv_data bcm2711_pv3_data = {
 	.fifo_depth = 64,
 	.pixels_per_clock = 1,
 	.encoder_types = {
-		[0] = VC4_ENCODER_TYPE_VEC,
+		[PV_CONTROL_CLK_SELECT_VEC] = VC4_ENCODER_TYPE_VEC,
 	},
 };