drm/hisilicon: Fix spelling of clock in hisi-ade.txt

Signed-off-by: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: Xinliang Liu <xinliang.liu@linaro.org>
Cc: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Cc: trivial@kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1481894701-4613-1-git-send-email-pmeerw@pmeerw.net