drm/amd/display: Skip inactive planes within ModeSupportAndSystemConfiguration

[Why]
Coverity reports Memory - illegal accesses.

[How]
Skip inactive planes.
Reviewed-by: Alex Hung <alex.hung@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c

@@ -1099,8 +1099,13 @@ void ModeSupportAndSystemConfiguration(struct display_mode_lib *mode_lib)
 
 	// Total Available Pipes Support Check
 	for (k = 0; k < mode_lib->vba.NumberOfActivePlanes; ++k) {
-		total_pipes += mode_lib->vba.DPPPerPlane[k];
 		pipe_idx = get_pipe_idx(mode_lib, k);
+		if (pipe_idx == -1) {
+			ASSERT(0);
+			continue; // skip inactive planes
+		}
+		total_pipes += mode_lib->vba.DPPPerPlane[k];
+
 		if (mode_lib->vba.cache_pipes[pipe_idx].clks_cfg.dppclk_mhz > 0.0)
 			mode_lib->vba.DPPCLK[k] = mode_lib->vba.cache_pipes[pipe_idx].clks_cfg.dppclk_mhz;
 		else