[media] coda: allocate bitstream ringbuffer only for BIT decoder

The BIT encoder does not use a per-context bitstream ringbuffer as it encodes
directly into the videobuf2 capture queue's buffers. Avoid allocation of the
bitstream ringbuffer for encoder contexts.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/coda/coda-common.c

@@ -1689,7 +1689,8 @@ static int coda_open(struct file *file)
 			v4l2_err(&dev->v4l2_dev, "failed to allocate parabuf");
 			goto err_dma_alloc;
 		}
-
+	}
+	if (ctx->use_bit && ctx->inst_type == CODA_INST_DECODER) {
 		ctx->bitstream.size = CODA_MAX_FRAME_SIZE;
 		ctx->bitstream.vaddr = dma_alloc_writecombine(
 				&dev->plat_dev->dev, ctx->bitstream.size,