linux

This adds the required code to support field decoding. While most of
the code is derived from Rockchip and VSI reference code, the
reduction of the reference list to 16 entries has been found by
trial and errors. The list consist of all the references with the
opposite field parity.

The strategy being to deduplicate the reference picture that points
to the same storage (same index). The choice of opposite parity has
been made to keep the other field or a field pair to be kept in the
list. This method may not be robust if a field was lost.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>