media: venus: avoid multiple core dumps

Core dump is generated whenever there is system error reported
by firmware. Right now, multiple such dumps are generated if
recovery fails in first attempt, since the sys error handler is
invoked again for every failed recovery.
To avoid it, add conditional check to generate core dump only
once during every system error notification from firmware.

Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: document new dump_core field]