drm/vc4: dsi: Add configuration for BCM2711 DSI1

Commit d0666be8 upstream.

BCM2711 DSI1 doesn't have the issue with the ARM not being
able to write to the registers, therefore remove the DMA
workaround for that compatible string.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20201203132543.861591-8-maxime@cerno.tech