drm/qxl: drop WARN_ONCE()

There is no good reason to flood the kernel log with a WARN
stacktrace just because someone tried to mmap a prime buffer.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20190524104251.22761-1-kraxel@redhat.com

drivers/gpu/drm/qxl/qxl_prime.c

@@ -77,6 +77,5 @@ void qxl_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
 int qxl_gem_prime_mmap(struct drm_gem_object *obj,
 		       struct vm_area_struct *area)
 {
-	WARN_ONCE(1, "not implemented");
 	return -ENOSYS;
 }