Specializing socket class to CAN socket operations.

Specializing socket class to CAN socket operations.

Move all legacy opening RAW CAN socket operation to socket class. Each operations
on a CAN socket has to be simple and made by the socket class.
Simple BCM socket open operation is implemented.
Future will be to open specialized BCM CAN sockets on demand.

Change-Id: If285b97afb9871245ab1f13cd9f0401fbd9adf95
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>