ARM: dts: msm: move PMI8998 devices into overlays for sdm845

Move the PMI8998 device nodes and their consumer usage into board
specific device tree overlay files.  This ensures that the
optional PMI8998 devices do not show up in the base SDM845 device
tree.

Change-Id: I6bd9f714ad85a65f2787c3eb0c63c43711481cdf
Signed-off-by: David Collins <collinsd@codeaurora.org>