drm/i915/display: Fix sel fetch plane offset calculation

skl_calc_main_surface_offset() is used to calculate an aligned plane
surface address considering the inner framebuffer x and y offset.
It can not be used by selective fetch functions becase there is no
PLANE_SEL_FETCH_SURF.
So the PLANE_SEL_FETCH_OFFSET.y should only be PLANE_OFFSET.y +
damaged_area_within_plane.y1.

This fixes glitches seen in fbcon caused by typing something in
the terminal.

BSpec: 55229
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210815014346.373945-1-jose.souza@intel.com