drm/scdc-helper: Convert errors into debug messages

drm/scdc-helper: Convert errors into debug messages

Since we may attempt to reconfigure SCDC when the sink has already been
disconnected we probably shouldn't scare the user with errors in dmesg
that are 100% expected in that case. Just leave it up to the caller
whether to print an error message or not, and just output debug
messages from the helper itself.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180323182537.30784-1-ville.syrjala@linux.intel.com
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>