gpu: ion: Add support for secure buffers

Secure buffers provides a way to allow premium encrypted
multimedia content to be decrypted in a secured
memory area that does not allow for interception of the
decrypted content.

Add support for heap type that allow heap to be
used for content protection. Introduce new content
protection heap type and id's.

Change-Id: Idd56aa8805b5b74d1b9ab3fe8964aacc218668c1
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
[sboyd: drop board file and scm.h changes]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>