nsure sensible constraints.

References: https://bugzilla.stlinux.com/show_bug.cgi?id=11229
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Reviewed-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
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