drm/amd/display: Use requested HDMI aspect ratio

[Why]
The DRM mode's HDMI picture aspect ratio field was never saved in
dc_stream's timing struct. This causes us to mistake a new stream to
have the same timings as the old, even though the user has requested a
different aspect ratio.

[How]
Save DRM's aspect ratio field within dc_stream's timing struct.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=107153


Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Mikita Lipski <Mikita.Lipski@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org