ASoC: msm8996: remove unused internal BT mixer command

Internal Bluetooth is not supported in MSM8996 target. Remove
unused mixer control for internal Bluetooth sample rate setting.

Change-Id: I197432c203f9ba9dbc5f4cbe5fe0d246d264ad50
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>