Revert "Revert "net: introduce CAN specific pointer in the struct net_device""

This reverts commit 3b217c7f as there
is no more need to keep the KABI stable at this point in time.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I44693a2137095715d5e5c064ed83cf7e8675e748