drm/amd/display: Skip inactive planes within ModeSupportAndSystemConfiguration

commit a54f7e86 upstream.

[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>
[get_pipe_idx() was introduced as a helper by
dda4fb85 ("drm/amd/display: DML changes for DCN32/321") in v6.0.
This patch backports it to make code clearer. And minor conflict is
resolved due to code context change.]
Signed-off-by: Jianqi Ren <jianqi.ren.cn@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>