drm/i915/display: remove duplicated assignment to pointer crtc_state

Pointer crtc_state is being assigned twice, one of these is redundant
and can be removed.

Addresses-Coverity: ("Evaluation order violation")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210144535.341977-1-colin.king@canonical.com