Bluetooth: shell: Split BR/EDR commands

This splits BR/EDR command under 'bt' to 'br' to reduce the command
list and at same time cleaning the mix between different bearers.

In addition to that also remove "br-" prefix for the commands:

br - Bluetooth BR/EDR shell commands
Options:
  -h, --help  :Show command help.
Subcommands:
  auth-pincode       :<pincode>
  connect            :<address>
  discovery          :<value: on, off> [length: 1-48] [mode: limited]
  iscan              :<value: on, off>
  l2cap-register     :<psm>
  oob                :
  pscan              :value: on, off
  sdp-find           :<HFPAG>
  rfcomm-register    :<channel>
  rfcomm-connect     :<channel>
  rfcomm-send        :<number of packets>
  rfcomm-disconnect  :[none]

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>