can: mark bittiming_const pointer in struct can_priv as const

This patch marks the bittiming_const pointer as in the struct can_pric as
"const". This allows us to mark the struct can_bittiming_const in the CAN
drivers as "const", too.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/can/ti_hecc.c b/drivers/net/can/ti_hecc.c
index 4accd7e..527dbcf 100644
--- a/drivers/net/can/ti_hecc.c
+++ b/drivers/net/can/ti_hecc.c
@@ -196,7 +196,7 @@
 #define HECC_CANGIM_SIL		BIT(2)	/* system interrupts to int line 1 */
 
 /* CAN Bittiming constants as per HECC specs */
-static struct can_bittiming_const ti_hecc_bittiming_const = {
+static const struct can_bittiming_const ti_hecc_bittiming_const = {
 	.name = DRV_NAME,
 	.tseg1_min = 1,
 	.tseg1_max = 16,