slimbus: Add snapshot of slimbus driver

This snapshot is taken as of msm-4.14 'commit <1572d8323c96>
(Merge "soc: qcom: use interruptible wait in cdsprm for rpmsg messages")'.

Change-Id: I06c84ae568d88f98435fddbbb74a9db6dbb59109
Signed-off-by: Dilip Kota <dkota@codeaurora.org>