It is fine for displays without audio functionality to not provide
any SAD block in their EDID. Do not log an error in that case,
just return quietly.

This fixes half of bug fdo#107825:
https://bugs.freedesktop.org/show_bug.cgi?id=107825Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Signed-off-by: NJean Delvare <jdelvare@suse.de>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>