It's perfectly valid for an ELD to contain no SADs. This simply means that
only basic audio is supoprted.

In this case, we still want to limit a PCM's capabilities based on the ELD.

History:

* Originally, ELD application was limited solely by sad_count>0, which
  was used to check that an ELD had been read.
* Later, eld_valid was added to the conditions to satisfy.

This change removes the original sad_count>0 check, which when squashed
with the above two changes ends up replacing if (sad_count) with
if (eld_valid).
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>