bridge_native_rtp.c: Fix direct media video RTP instance ACL check.

The video stream was using the audio stream RTP instance addresses to
check if the video RTP gets directed to an allowed direct media Access
Control List (ACL) address.  There is no guarantee that the video RTP
instance uses the same addresses as the audio RTP instance.

This looks like it has been a bug since v11 when direct media ACL was
first added to chan_sip and then faithfully reproduced through a couple
code refactorings into the new bridging architecture.

Change-Id: I8ddd56320e0eea769f3ceed3fa5b6bdfb51d681a