Add support of DRM_FORMAT_MOD_LINEAR modifier.

Signed-off-by: Mickael Reulier <mickael.reulier@st.com>
Signed-off-by: Yannick Fertré <yannick.fertre@st.com>
Acked-by: Philippe Cornu <philippe.cornu@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1554283514-2960-1-git-send-email-yannick.fertre@st.com


Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>