msm: kgsl: Disable graphics content protection for SDM429

Disable GPU content protection for SDM429. Secure
memory is allocated from CMA which reserves around
100MB which is terrible idea for low memory targets
like SDM429 and hence disable it.

Change-Id: I1637437888b3f8fc56c9389accbd31cb15fd1b80
Signed-off-by: Sunil Khatri <sunilkh@codeaurora.org>