ipod6g: add hardware H.264 video playback

Add S5L8702 VPU-B initialization, reset, bitstream input, frame output,
and cache maintenance to the iPod 6G target. Advertise it with
HAVE_HW_H264 and append a capability-gated decoder interface to the
plugin API.

Keep MP4 parsing, AAC decode and mixer output, A/V synchronization,
playback controls, resume state, and presentation in the multi-file
h264_player plugin. The target layer exposes decoder operations only.

Accept non-fragmented MP4/M4V containing Constrained Baseline H.264
through level 3.0, up to 640x480 at 30 fps, with optional AAC-LC audio.
Validate codec configuration and all sample-table relationships before
activating the hardware.

Read MP4 tables in bulk, boost the CPU while preparing them, and report
staged loading progress so long movies do not appear to hang during
startup.

Register the viewer and document its format limits and controls. The
libm4a compatibility fixes needed by video-first containers remain in
the preceding standalone change.

Tested on an iPod Classic 6G through an isolated Rolo nightly runtime:
H.264/AAC playback and M4V startup succeeded. Normal and
isolated-runtime iPod 6G builds also complete, and git diff --check is
clean.

Change-Id: I1e96c65c7d0b4231a94f602f8052f1b26d6e4a80

apps/plugin.h

@@ -83,6 +83,9 @@ int plugin_open(const char *plugin, const char *parameter);
 #include "metadata.h"
 #include "sound.h"
 #include "audio.h"
+#ifdef HAVE_HW_H264
+#include "hw_h264.h"
+#endif
 #include "voice_thread.h"
 #include "root_menu.h"
 #include "talk.h"
@@ -179,7 +182,7 @@ int plugin_open(const char *plugin, const char *parameter);
  * when this happens please take the opportunity to sort in
  * any new functions "waiting" at the end of the list.
  */
-#define PLUGIN_API_VERSION 284
+#define PLUGIN_API_VERSION 285
 
 /* 239 Marks the removal of ARCHOS HWCODEC and CHARCELL */
 
@@ -1046,6 +1049,9 @@ struct plugin_api {
                                    const struct viewport *vp);
     int (*gesture_flick_get)(const struct gesture_event *gevt);
 #endif
+#ifdef HAVE_HW_H264
+    const struct hw_h264_api *hw_h264;
+#endif
 };
 
 /* plugin header */