ARM: dts: msm: Add flag to identify CP mode for msmtitanium

A secure video session can be configured in different
modes to acheive the desired level of security. This
string can distinguish for the secure mode for any
given target.

Change-Id: I9dafd693c6228bff71e6112516827f8e6d87960c
Signed-off-by: Srinu Gorle <sgorle@codeaurora.org>