msm: vidc: Fix SYS_ERROR handling

Do not clean the session while handling sys error, instead
only set the instance state to invalid and report the error to client.
The session will be cleaned as part of vidc_close.

CRs-Fixed: 755740
Change-Id: Iaa1bc9a39c51be67649830bf9cb6acdbce105211
Signed-off-by: Sowmya Pandiri <spandiri@codeaurora.org>