drm/mxsfb: Use gem_free_object_unlocked

CMA helpers are struct_mutex free, and so is the mxsfb itself. And
that's the only valid reason for using gem_free_object.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Marek Vasut <marex@denx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20170717151045.4188-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/mxsfb/mxsfb_drv.c

@@ -334,7 +334,7 @@ static struct drm_driver mxsfb_driver = {
 	.irq_uninstall		= mxsfb_irq_preinstall,
 	.enable_vblank		= mxsfb_enable_vblank,
 	.disable_vblank		= mxsfb_disable_vblank,
-	.gem_free_object	= drm_gem_cma_free_object,
+	.gem_free_object_unlocked = drm_gem_cma_free_object,
 	.gem_vm_ops		= &drm_gem_cma_vm_ops,
 	.dumb_create		= drm_gem_cma_dumb_create,
 	.dumb_map_offset	= drm_gem_cma_dumb_map_offset,