[rtcp] Fir/Sli/Rpsi updated not to use RTCPUtility

BUG=webrtc:5260

Review-Url: https://codereview.webrtc.org/2023803002
Cr-Original-Commit-Position: refs/heads/master@{#12965}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0fc37d7dec48d5c66c583035b1090d466cc4a8a2
11 files changed