drm/vc4: drv: Support BCM2711

The BCM2711 has a reworked display pipeline, and the load tracker needs
some adjustment to operate properly. Let's add a compatible for BCM2711
and disable the load tracker until properly supported.

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/beac4f9ef0261bca731a0402c8354e9af740519c.1599120059.git-series.maxime@cerno.tech