ARM: dts: msm: Add support for 400MHz as ACPU for MDM9607

Add 400MHz in the speed-bin and cpufreq node to support it as a scaling
and available frequency for cpu clock. Update the frequency of 806.4MHz to
be now derived from GPLL0.

Change-Id: I9e3edd6564935c7bdfadd109e5652a81b3d8b2b6
Signed-off-by: Jaydeep Sen <jsen@codeaurora.org>