[Why]
The kms_plane@plane-position-covered-pipe-*-planes subtests can produce
a sequence of atomic commits such that neither active_changed nor
mode_changed but connectors_changed.

When this happens we remove the old stream from the context and add
a new stream but the new stream doesn't have mode_changed=true set.

This incorrect programming sequence causes CRC mismatches to occur in
the test.

The stream->mode_changed value should be set whenever a new stream
is created.

[How]
A new stream is created whenever drm_atomic_crtc_needs_modeset is true.
We previously covered the active_changed and mode_changed conditions
for the CRTC but connectors_changed is also checked within
drm_atomic_crtc_needs_modeset.

So just use drm_atomic_crtc_needs_modeset directly to determine the
mode_changed flag.
Signed-off-by: NNicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: NSun peng Li <Sunpeng.Li@amd.com>
Acked-by: NBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>