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

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

Change-Id: I00264ef151997a6365dd438b3676eb0c808b2de0
Signed-off-by: David Collins <collinsd@codeaurora.org>