ARM: dts: msm: Offline 1GB of 6GB DDR for Atoll

Current now we're not allowing page cache allocating from Movable
Zone, hence 2GB Movable zone will significantly reduce page cache
size. To avoid impacting launch latency, reduce the size of Movable
Zone to 1GB.

Change-Id: I0b53dd188c0ad6086cc42b5ce19b3718a80217c8
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>