ARM: dts: msm: Move 8994 Interposer BLSP definitions

The BLSP alias definitions and property overrides on the
MSM8994 Interposer platforms are actually specific to 8974.
Move these overrides into interposer-specific DTS files so
that generic 8994-specific DTS files can be created.

Change-Id: I3eb3d3d2e961786af0321071a4eb3d26e650ca95
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>