dt-bindings: display: Add support for the BCM2711 HVS

The HVS found in the BCM2711 is slightly different from the previous
generations, let's add a compatible for it.

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: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/a6b4c9ee03bc8f950adc6c493db70cd540c2f902.1599120059.git-series.maxime@cerno.tech