drm/vc4: plane: Fix margin calculations for the right/bottom edges

drm/vc4: plane: Fix margin calculations for the right/bottom edges

[ Upstream commit e3f6e40a5e0a2dd5ddfca98963fdd4b7bc76a70d ]

The current plane margin calculation code clips the right and bottom
edges of the range based using the left and top margins.

This is obviously wrong, so let's fix it.

Fixes: 188f608deb8f ("drm/vc4: Take margin setup into account when updating planes")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-6-maxime@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Sasha Levin <sashal@kernel.org>