can: ti_hecc: ti_hecc_mailbox_read(): remove set but not used variable 'mbx_mask'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/can/ti_hecc.c: In function 'ti_hecc_mailbox_read':
drivers/net/can/ti_hecc.c:533:12: warning:
 variable 'mbx_mask' set but not used [-Wunused-but-set-variable]

It is never used so can be removed.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/ti_hecc.c

@@ -526,9 +526,8 @@ static unsigned int ti_hecc_mailbox_read(struct can_rx_offload *offload,
 					 u32 *timestamp, unsigned int mbxno)
 {
 	struct ti_hecc_priv *priv = rx_offload_to_priv(offload);
-	u32 data, mbx_mask;
+	u32 data;
 
-	mbx_mask = BIT(mbxno);
 	data = hecc_read_mbx(priv, mbxno, HECC_CANMID);
 	if (data & HECC_CANMID_IDE)
 		cf->can_id = (data & CAN_EFF_MASK) | CAN_EFF_FLAG;