Adds helper functions to count HCI devs and process A2MP Discover
Request, code makes sure that first controller in the list is
BREDR one. Trace is shown below:

...
> ACL data: handle 11 flags 0x02 dlen 16
    A2MP: Discover req: mtu/mps 670 mask: 0x0000
< ACL data: handle 11 flags 0x00 dlen 22
    A2MP: Discover rsp: mtu/mps 670 mask: 0x0000
      Controller list:
        id 0 type 0 (BR-EDR) status 0x01 (Bluetooth only)
        id 1 type 1 (802.11 AMP) status 0x01 (Bluetooth only)
...
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Placeholder for future A2MP Command Reject handler.
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Implement basic processing for AMP Manager Protocol (A2MP).

Example below shows processing unrecognized command.
...
> ACL data: handle 11 flags 0x02 dlen 12
    A2MP: code 0x00 ident 3 len 0
< ACL data: handle 11 flags 0x00 dlen 14
    A2MP: Command Reject: reason (0) - Command not recognized
...
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Add L2CAP chan ops callbacks.
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Helper function to build and send A2MP messages.
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Define AMP Manager and some basic functions.
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

Create and initialize fixed A2MP channel
Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>