media: hantro: Enable HOLD_CAPTURE_BUF for H.264

This is needed to optimize field decoding. Each field will be
decoded into the same capture buffer. To be able to queue multiple
buffers, we need to be able to ask the driver to hold the capture
buffer.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Sebastian Fricke <sebastian.fricke@collabora.com>