drm/amd/display: Update swizzle mode enums

[Why]
Swizzle mode enum for DC_SW_VAR_R_X was existing,
but not mapped correctly.

[How]
Update mapping and conversion for DC_SW_VAR_R_X.

Reviewed-by: XiangBing Foo <[e-mail]>
Reviewed-by: Martin Leung <[e-mail]>
Acked-by: Qingqing Zhuo <[e-mail]>
Signed-off-by: Alvin Lee <[e-mail]>
Cc: [e-mail]
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

···
 	case DC_SW_VAR_D_X:
 		*sw_mode = dm_sw_var_d_x;
 		break;
-
+	case DC_SW_VAR_R_X:
+		*sw_mode = dm_sw_var_r_x;
+		break;
 	default:
 		ASSERT(0); /* Not supported */
 		break;

drivers/gpu/drm/amd/display/dc/dml/display_mode_enums.h

···
 	dm_sw_SPARE_13 = 24,
 	dm_sw_64kb_s_x = 25,
 	dm_sw_64kb_d_x = 26,
-	dm_sw_SPARE_14 = 27,
+	dm_sw_64kb_r_x = 27,
 	dm_sw_SPARE_15 = 28,
 	dm_sw_var_s_x = 29,
 	dm_sw_var_d_x = 30,
-	dm_sw_64kb_r_x,
+	dm_sw_var_r_x = 31,
 	dm_sw_gfx7_2d_thin_l_vp,
 	dm_sw_gfx7_2d_thin_gl,
 };