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 --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index f9cd247..2571082 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -181,13 +181,13 @@
 	/* make sure bottom-up buffers are properly displayed */
 	if (tegra_fb_is_bottom_up(fb)) {
 		value = tegra_dc_readl(dc, DC_WIN_WIN_OPTIONS);
-		value |= INVERT_V;
+		value |= V_DIRECTION;
 		tegra_dc_writel(dc, value, DC_WIN_WIN_OPTIONS);
 
 		v_offset += fb->height - 1;
 	} else {
 		value = tegra_dc_readl(dc, DC_WIN_WIN_OPTIONS);
-		value &= ~INVERT_V;
+		value &= ~V_DIRECTION;
 		tegra_dc_writel(dc, value, DC_WIN_WIN_OPTIONS);
 	}
 
@@ -578,7 +578,7 @@
 	}
 
 	if (window->bottom_up)
-		value |= INVERT_V;
+		value |= V_DIRECTION;
 
 	tegra_dc_writel(dc, value, DC_WIN_WIN_OPTIONS);