linux-imx

drm/sti: do not set gdp pixel clock rate if mode is not set

Fix a division by 0 case : in some cases, when the GDP plane is being
disabled atomic_check() is called with "mode->clock = 0".
In that case, do not set parent and pixel clock rate.

Signed-off-by: Vincent Abriou <vincent.abriou@st.com>