drm/amd/display: Set test_pattern_changed update flag on pipe enable

drm/amd/display: Set test_pattern_changed update flag on pipe enable

[Why]
In certain cases, ODM pipe split can occur while stream already has test
pattern enabled. The new pipe used in the ODM combine config must be
configured to output the test pattern in this case.

[How]
If the stream is configured to output test pattern, then set the
test_pattern_changed update flag for the new pipe when it gets enabled.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>