drm: Set connector DPMS status to ON in drm_crtc_helper_set_config

When setting a new crtc configuration, force the DPMS state of all
connectors to ON. Otherwise, they'll be left at OFF and a future mode set
that disables the specified connector will not turn the connector off.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>