rtp-amr.adoc: TCH/AFS Uplink
rtp-amr.adoc: TCH/AFS Uplink

Add new chapter by Nutaq for Speech Frame Following a SID_FIRST frame

Change-Id: Ib7cfb07525ea311d9dac051a6e139b0ae0549504

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts