drm/i915/scaler: remove id in favor of scaler_id

drm/i915/scaler: remove id in favor of scaler_id

id is not really used anywhere in skl_scaler_get_config(). Replace it
with scaler_id.

Return if no scaler was found.

v1->v2
- check if any scaler was found (Ville)

Cc: Nemesa Garg <nemesa.garg@intel.com>
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Michał Grzelak <michal.grzelak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260509164048.627399-7-michal.grzelak@intel.com