lib/chv: CHV media pipeline command sequence

lib/chv: CHV media pipeline command sequence

Enable gem_media_fill test for CHV platform.  In addition to differences in
media IP blocks from Broadwell, the command sequence also differs for
programming the media pipeline, e.g., should not send a MEDIA_STATE_FLUSH
right before the MI_BATCH_BUFFER_END of batch buffers using MEDIA_OBJECT.
Uses explicit IS_BROADWELL / IS_CHERRYVIEW to distinguish in gen8 media
fill handling.

Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
Reviewed-by: Xiang, Haihao <haihao.xiang@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>