msm: mdss: hdmi: validate HDMI EDID's max number of CEA blocks

No upper-bound validation is performed when reading number of
extended CEA blocks from the untrusted source (EDID). Add a check
to limit the number of CEA extension blocks.

Change-Id: I69f09ed0ad28a4c267cf3e8f7a12efe46f75e244
Signed-off-by: Narender Ankam <nankam@codeaurora.org>