ARM: dts: msm: update frame threshold time for atoll

Change adds 800 microseconds as frame threshold time
for atoll as posted start feature enables us to have
lower threshold time.

Change-Id: I67cbc612270f866ec40a99aba200d03abe48c7cd
Signed-off-by: Bruce Hoo <bingchua@codeaurora.org>
Signed-off-by: Ray Zhang <rayz@codeaurora.org>