drm/amd: be quiet when no SAD block is found

drm/amd: be quiet when no SAD block is found

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=107825

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jean 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: Alex Deucher <alexander.deucher@amd.com>