msm: sde: allow offline session to wait for inline closing

Add delay during session open to wait for any inline
session to close. This enables smooth inline-offline
transition, avoiding race condition such that inline
session is still in process of closing while a new
offline session is opening.

Change-Id: I0fa2a973e4ec7f7c670b0a7fb94c088e41f145ec
Signed-off-by: Alan Kwong <akwong@codeaurora.org>