drm/amd/display: avoid large stack allocation in commit_planes_do_stream_update_sequence

drm/amd/display: avoid large stack allocation in commit_planes_do_stream_update_sequence

The function has two arrays on the stack to hold temporary dsc_optc_config
and dsc_config objects. The combination blows through common stack frame
warning limits in combination with the other local variables:

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:4070:22: error: stack frame size (1352) exceeds limit
      (1280) in 'commit_planes_do_stream_update_sequence' [-Werror,-Wframe-larger-than]

Since neither array is initialized or used outside of the
add_link_update_dsc_config_sequence() function, there is no actual
need to keep each element around.

Replace the arrays with a single instance each to reduce the stack usage
to less than half.

Fixes: 9f49d3cd7e71 ("drm/amd/display: Implement block sequencing infrastructure for modular hardware operations.")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Acked-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>