Stub the wcnss_ctrl API to allow compile testing wcnss function drivers.

Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: NAndy Gross <andy.gross@linaro.org>
Signed-off-by: NAndy Gross <andy.gross@linaro.org>