ARM: dts: msm: add SPMI PMIC arbiter device for atoll

Add SPMI PMIC arbiter device so that it is possible to
communicate with PMICs attached to SPMI bus.

Change-Id: I78ddd2e8b7b4e5416191ab79c3d59c2ae4996d5d
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>