[rc_v2]: Support avbr ratecontrol

when select avbr must set target_bps max_bps min_bps,in still scene
will used min_bps for enc, in the moving scene will max_bps for enc.
and final avg bit will get close to target_bps

Change-Id: I84b2878c7e76b18a593ca2a0d99c0c8f26a2d557
Signed-off-by: sayon.chen <sayon.chen@rock-chips.com>

inc/rk_venc_cmd.h

@@ -168,6 +168,7 @@ typedef enum MppEncRcMode_e {
     MPP_ENC_RC_MODE_VBR,
     MPP_ENC_RC_MODE_CBR,
     MPP_ENC_RC_MODE_FIXQP,
+    MPP_ENC_RC_MODE_AVBR,
     MPP_ENC_RC_MODE_BUTT
 } MppEncRcMode;