ion: msm: Add support for VMID_CP_DSP_EXT

Add necessary flags for userspace to request this type of memory.

Change-Id: I4d123f45dde9a191d79bd39c3e16cfaddf39a875
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>