drm/atomic: Remove drm_atomic_connectors_for_crtc.

drm/atomic: Remove drm_atomic_connectors_for_crtc.

BugLink: http://bugs.launchpad.net/bugs/1542939
Now that connector_mask is reliable there's no need for this
function any more.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1451908400-25147-6-git-send-email-maarten.lankhorst@linux.intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(back ported from commit 14de6c44d149c68df1800ded42bbab51485ef67a)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Conflicts:
	drivers/gpu/drm/drm_atomic.c
	drivers/gpu/drm/drm_atomic_helper.c

Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>