drm/i915/glk: Fix Geminilake scalers mode programming

Geminilake scalers can do 7x7 filtering for all supported input sizes,
so it doesn't need the "high quality" mode programming, which was
actually removed from that platform.

v2: Split dev_priv parameter change out. (Ville)
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>,
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170223071600.14356-5-ander.conselvan.de.oliveira@intel.com