can: add TI CAN (HECC) driver

TI HECC (High End CAN Controller) module is found on many TI devices. It
has 32 hardware mailboxes with full implementation of CAN protocol 2.0B
with bus speeds up to 1Mbps. Specifications of the module are available
on TI web <http://www.ti.com>

Signed-off-by: Anant Gole <anantgole@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>