ARM: dts: msm: Add default prefetching size for secure playback

Prefetching for heaps designated for secure playback provides a
good performance boost. Add the optimized default prefetching
size for clients to use.

Change-Id: If8f5ecda5058d1142b1c4dfcdb5bbf7947f4e62c
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>