msm: adsprpc: return fastrpc ioctl call if process exit sequence start

Added check to return fastrpc ioctl call when process exit sequence is
in progress.

Change-Id: I83915cb3fb75cc69d245a56800dcf42b492e01ea
Acked-by: Nishant Chaubey <chaubey@qti.qualcomm.com>
Signed-off-by: Jeya R <jeyr@codeaurora.org>