ARM: dts: msm: Support boards with PMK8001 PMIC for msm8996

Some MSM8996 boards will employ the PMK8001 PMIC. Introduce
msm-pmk8001.dtsi which defines the PMIC peripherals Linux may need
to communicate with. In addition, introduce the board level files
whose hierarchy include the corresponding qcom,pmic-id so that
the bootloader is able to pick compatible DTB blobs on boards which
use PMK8001.

Change-Id: I1d5f9c2422efef68f7a4a174c47a1e065bfa989a
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>