msm: mdss: fix crash when wrong params are passed on the esd config

If wrong parameters are set on the dtsi to configure the
esd, a null pointer access can happen. Fix this to make
sure we check for valid pointers and otherwise just
throw an error, but not access an invalid pointer.

Change-Id: I3df0889c1225dcb613910cb90f050a2994f5834d
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>