sound/oss/vidc.c: change the field used with DMA_ACTIVE

The constant DMA_ACTIVE is defined with the dma_buffparams structure rather
than with the audio_operations structure.  Takashi Iwai suggested that the
dmap_out field of the audio_operations structure should be used instead.

This is not tested.

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>