Revert "drm/i915: Use crtc_state->active in primary check_plane func"

This reverts commit dec4f799.

Jörg Otte reports a NULL pointder dereference due to this commit, as
'crtc_state' very much can be NULL:

        crtc_state = state->base.state ?
                intel_atomic_get_crtc_state(state->base.state, intel_crtc) : NULL;

So the change to test 'crtc_state->base.active' cannot possibly be
correct as-is.

There may be some other minimal fix (like just checking crtc_state for
NULL), but I'm just reverting it now for the rc2 release, and people
like Daniel Vetter who actually know this code will figure out what the
right solution is in the longer term.

Reported-and-bisected-by: Jörg Otte <jrg.otte@gmail.com>
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>