Removed the feeding_init call from tA2DP_ENCODER_INTERFACE

The feeding_init call is not used anymore - it has been superseded
by the newer A2dpCodecs.setCodecAudioConfig() mechanism.

Also, moved aptx_init_framing_params() and aptx_hd_init_framing_params()
calls to the corresponding encoder_update functions.

Test: A2DP streaming to Bluetooth headsets
Change-Id: I52f42b4701d04fe2ddb8f115bb9cd57fe38e2b38