drm/mm: Don't WARN if drm_mm_reserve_node

Jesse's BIOS fb reconstruction code actually relies on the -ENOSPC
return value to detect overlapping framebuffers (which the bios uses
always when lighting up more than one screen). All this fanciness
happens in intel_alloc_plane_obj in intel_display.c.

Since no one else uses this we can safely remove the WARN without
repercussions.

Reported-by: Ben Widawsky <[e-mail]>
Tested-by: Ben Widawsky <[e-mail]>
Cc: Jesse Barnes <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Acked-by: Dave Airlie <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/drm_mm.c

···
 		return 0;
 	}
 
-	WARN(1, "no hole found for node 0x%lx + 0x%lx\n",
-	     node->start, node->size);
 	return -ENOSPC;
 }
 EXPORT_SYMBOL(drm_mm_reserve_node);