drm/vc4: txp: Add horizontal and vertical size offset toggle bit

drm/vc4: txp: Add horizontal and vertical size offset toggle bit

The new writeback controllers that can be found on the BCM2712 require
to have their horizontal and vertical size reduced by one.

Let's tie that behaviour to the compatible so we can support both the
new and old controllers.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241025-drm-vc4-2712-support-v2-16-35efa83c8fc0@raspberrypi.com
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>