The A2MP protocol uses a reliable ERTM channel to coordinate high-speed AMP channels between two Bluetooth devices. This is done using a fixed channel ID, but ERTM carries a lot of state so the existing approach of hard-coded fixed channel handlers does not work. This adds hooks for creation and use of fixed channel sockets for use within the kernel. Change-Id: I27363b7882ffc8ec643ffe792b078f253700089b Signed-off-by: Mat Martineau <mathewm@codeaurora.org>