V4L/DVB (5675): Move big PIO accesses from the interrupt handler to a workhandler

Sliced VBI transfers use PIO instead of DMA. This was done inside the
interrupt handler, but since PIO accesses are very slow this meant that
a lot of time was spent inside the interrupt handler. All PIO copies are
now moved to a workqueue. This should fix various issues with missing time
ticks and remote key hits.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/video/ivtv/ivtv-driver.c b/drivers/media/video/ivtv/ivtv-driver.c
index e29f949..efc6635 100644
--- a/drivers/media/video/ivtv/ivtv-driver.c
+++ b/drivers/media/video/ivtv/ivtv-driver.c
@@ -652,6 +652,7 @@
 	itv->dma_timer.data = (unsigned long)itv;
 
 	itv->cur_dma_stream = -1;
+	itv->cur_pio_stream = -1;
 	itv->audio_stereo_mode = AUDIO_STEREO;
 	itv->audio_bilingual_mode = AUDIO_MONO_LEFT;