disp: msm: dp: validate edid before dereferencing

BugLink: https://bugs.launchpad.net/bugs/1945470



Currently, when using custom edid from debugfs, the
extensions data inside the edid block is not validated
before dereferencing the extension block.

The fix adds a edid validation function to validate
any custom edids before accessing any members in the
edid block.

Change-Id: I65e596cd6743febd5d55d968908619ebd50bef29
Signed-off-by: osaisruj <osaisruj@codeaurora.org>
(cherry picked from commit ed39c03638f858590cb2f174bc0853976df43381)
Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>