msm: vidc: fix error handling during hardware overload error

when hardware overload error happens, session_abort gets called
multiple times as part of error handling and cleanup. This results
in firmware timing out for successive commands. Firmware timeout
sends sys_error to all clients causing all sessions to close. This
change cleans the last session and allows previous running sessions
to continue.

b/24065713

Change-Id: Ia7ab600af2345896a4bb17dc726d0bdc473f93fe
Signed-off-by: Ashray Kulkarni <ashrayk@codeaurora.org>