Pass dev_priv to intel_atomic_setup_scalers(). The next patch will need
a dev_priv pointer.

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/20170223071600.14356-4-ander.conselvan.de.oliveira@intel.com