drv: psb: check crtc pointer before calling in DPMS and mode set.

drv: psb: check crtc pointer before calling in DPMS and mode set.

Avoid the possibility of oops-ing the kernel by running the
test-opengl-fillrate test (and others) which bypass DRM_MASTER
authentication.

Typically the test will execute succesfully, however when
unblanking/un-suspending we NULL deref in gfx_late_resume()

Signed-off-by: Oliver McFadden <oliver.mcfadden@intel.com>
Reviewed-by: Pauli Nieminen <pauli.nieminen@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>