slim-msm-ngd: Register with specific subsystem

Slimbus master is present in different subsystem
on different tragets.
Register with specific subsystem as mentioned in
the device tree.

Change-Id: I1bee7fdd7578deedca8e4e43af9055b41b96d652
Signed-off-by: Dilip Kota <dkota@codeaurora.org>