msm: vidc_3x: Fix in handing SYS_ERROR

When there is a SYS_ERROR the instance object is getting
freed even before notifying the client causing the kernel
NULL pointer dereferece. To avoid this concurrency between
video close session and H/W error, unlocking the instance
lock after notifying the client.

Change-Id: I37027ffbf54143b89b93387e7cd5115b1bcfb71f
Signed-off-by: Mahesh Voorugonda <mvooru@codeaurora.org>