drm/nva3-/disp: fix hda eld writing, needs to be padded

Commits 0a9e2b95 (drm/nvd0/disp: move HDA codec setup to core) and
a4feaf4e (drm/nva3/disp: move hda codec handling to core) moved code
around but neglected to fill data up to 0x60 as before. This caused
/proc/asound/cardN/eld#3.0 to show eld_valid as 0. With this patch, that
file is again populated with the correct data.

See https://bugs.freedesktop.org/show_bug.cgi?id=67051



Reported-and-tested-by: Alex <alupu01@gmail.com>
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>