[media] media: mtk-jpeg: fix continuous log "Context is NULL"

[media] media: mtk-jpeg: fix continuous log "Context is NULL"

The symptom is continuous log "mtk-jpeg 18004000.jpegdec: Context is NULL"
in kernel log. It is because the error handling in irq doesn't clear
interrupt.

The calling flow like as below when issue happen
mtk_jpeg_device_run()
mtk_jpeg_job_abort()
  v4l2_m2m_job_finish() -> m2m_dev->curr_ctx = NULL;
mtk_jpeg_dec_irq()
  v4l2_m2m_get_curr_priv()
     -> m2m_dev->curr_ctx == NULL
     -> return NULL
log "Context is NULL"

There is race condition between job_abort() and irq. In order to simplify
code, don't want to add extra flag to maintain state, empty job_abort() and
clear interrupt before v4l2_m2m_get_curr_priv() in irq.

Signed-off-by: Minghsiu Tsai <minghsiu.tsai@mediatek.com>
Acked-by: Rick Chang <rick.chang@mediatek.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>