msm:adsprpc: Prevent use after free in fastrpc_set_process_info

Serialize kzalloc in fastrpc_set_process_info and prevent use
after free.

Change-Id: I02d62182a234ef40ce33165247fc578f6727d27a
Acked-by: Deepika Singh <dsi@qti.qualcomm.com>
Signed-off-by: Jeya R <jeyr@codeaurora.org>