drm/tegra: dc - Rename INVERT_V to V_DIRECTION

V_DIRECTION is the name of the field in the documentation, so use that
for consistency. Also add the H_DIRECTION field for completeness.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/tegra/dc.c
Simple merge

diff --cc drivers/gpu/drm/tegra/dc.h
Simple merge