ARM: dts: msm: Set 320MHz as minimum clock for msm8992

The core clock for CPP HW help to determine the vote for CPP.
The minimum clock value of 465MHz results in high vote from
CPP. In order to have optimal tradeoff between bus vote and
CPP HW performance, reduce it to be 320Mhz.

Change-Id: I0fad9cb85a8c10fe6215c358cd446857b9297941
Signed-off-by: Rajakumar Govindaram <rajakuma@codeaurora.org>