MFC r248061:

Import Linux commit a1b7736dac5f2d5876e68c47a0fce3f423840070
Author: Sascha Hauer <s.hauer@pengutronix.de>
Date:   Wed Feb 1 11:38:22 2012 +0100

    drm drm_fb_helper: destroy modes

    drm_setup_crtcs allocated modes using drm_mode_duplicate. Free
    them in drm_fb_helper_crtc_free.

    Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
    Signed-off-by: Dave Airlie <airlied@redhat.com>

Discussed with:	Konstantin Belousov (kib@)