drm: fix kernel-doc warnings for SCALING_FILTER

This patch fixes the following kernel-doc warnings:

    /home/simon/src/linux/Documentation/gpu/drm-kms:466: ./drivers/gpu/drm/drm_crtc.c:236: WARNING: Unexpected indentation.
    /home/simon/src/linux/Documentation/gpu/drm-kms:466: ./drivers/gpu/drm/drm_crtc.c:237: WARNING: Block quote ends without a blank line; unexpected unindent.
    /home/simon/src/linux/Documentation/gpu/drm-kms:472: ./drivers/gpu/drm/drm_blend.c:203: WARNING: Unexpected indentation.
    /home/simon/src/linux/Documentation/gpu/drm-kms:472: ./drivers/gpu/drm/drm_blend.c:204: WARNING: Block quote ends without a blank line; unexpected unindent.

Signed-off-by: Simon Ser <contact@emersion.fr>
Fixes: 5c759eda ("drm: Introduce plane and CRTC scaling filter properties")
Cc: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/zJEUxNx4GwiY4FnqlVsuXdAWuH624SQ9VfN54NeH5E@cp7-web-043.plabs.ch