A2DP: Enable SBC 48K sampling frequency for TARGET_FLOSS

Currently the sampling rate for SBC in A2DP source is hard-coded to
44100 hz. This makes it default to include 48K as well.

Bug: 333344362
Test: mmm packages/modules/Bluetooth
Tag: #floss
Flag: EXEMPT, Floss-only change

Change-Id: I3f3296d16aee109e75b4ea9d66d1721fbec44536