can: ti_hecc: Fix unintialized variable

In ti_hecc_xmit(), local variable "data" is not initialized before
being used.
This initialization got inadvertently removed in the following patch:

	can: Unify droping of invalid tx skbs and netdev stats

Acked-by: Anant Gole <anantgole@ti.com>
Signed-off-by: Abhilash K V <abhilash.kv@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>