drm/i915/sdvo: Initialize the encoder earlier

Call drm_encoder_init() earlier so that we don't have to keep passing
the i915/dev_priv around separately.

v2: Reorder drm_encoder_cleanup() in the error path (Jani)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230825134431.24391-3-ville.syrjala@linux.intel.com