can: ti hecc module : add platform specific initialization callback.

CAN module on AM3517 requires programming of IO expander as part
of init sequence - to enable CAN PHY. Added platform specific
callback to handle phy control(switch on /off).

Signed-off-by: Sriramakrishnan <srk@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>