drm/amd/display: Incorrect Mirror Cositing

[WHY]
hinit/vinit are incorrect in the case of mirroring.

[HOW]
Cositing sign must be flipped when image is mirrored in the vertical
or horizontal direction.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Samson Tam <samson.tam@amd.com>
Signed-off-by: Jesse Agate <jesse.agate@amd.com>
Signed-off-by: Brendan Leder <breleder@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Jesse Agate

drivers/gpu/drm/amd/display/dc/sspl/dc_spl.c

@@ -641,16 +641,16 @@ static void spl_calculate_inits_and_viewports(struct spl_in *spl_in,
 		/* this gives the direction of the cositing (negative will move
 		 * left, right otherwise)
 		 */
-		int sign = 1;
+		int h_sign = flip_horz_scan_dir ? -1 : 1;
+		int v_sign = flip_vert_scan_dir ? -1 : 1;
 
 		switch (spl_in->basic_in.cositing) {
-
 		case CHROMA_COSITING_TOPLEFT:
-			init_adj_h = spl_fixpt_from_fraction(sign, 4);
-			init_adj_v = spl_fixpt_from_fraction(sign, 4);
+			init_adj_h = spl_fixpt_from_fraction(h_sign, 4);
+			init_adj_v = spl_fixpt_from_fraction(v_sign, 4);
 			break;
 		case CHROMA_COSITING_LEFT:
-			init_adj_h = spl_fixpt_from_fraction(sign, 4);
+			init_adj_h = spl_fixpt_from_fraction(h_sign, 4);
 			init_adj_v = spl_fixpt_zero;
 			break;
 		case CHROMA_COSITING_NONE: