[media] [3.3.0] ir-raw: remove BUG_ON in ir_raw_event_thread

This patch removes BUG_ON in ir_raw_event_thread which IMO is a
over-kill, and this kills the ir_raw_event_thread too. With a bit of
additional logic in this patch, we nomore need to kill this thread.
Other disadvantage of having a BUG-ON is,
wake_up_process(dev->raw->thread) called on dead thread via
ir_raw_event_handle will result in total lockup in SMP system.

Advantage of this patch is ir-raw event thread is left in a usable state
even if the fifo does not have enough bytes.

This patch sets the thread into TASK_INTERRUPTIBLE if raw-fifo has less
then sizeof(struct ir_raw_event) bytes.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>