Simplify SBC encoder API

Currently it is unclear what the input, output, and configuration of
the SBC codec are. This patch refactors the use of the SBC_Encoder
function. Parameters for input and output are added, instead of passing
them in alongside the configuration.

Test: Tested A2DP playback
Change-Id: I755a022983f823475c14815cc0610f90a5fbc813