net: fec: do not access reserved register for i.MX6ULL

The MIB RAM and FIFO receive start register does not exist on
i.MX6ULL. Accessing these register will cause enet not work well or
cause system report fault.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>

drivers/net/fec_mxc.c

@@ -563,7 +563,7 @@ static int fec_init(struct eth_device *dev, bd_t *bd)
 	writel(0x00000000, &fec->eth->gaddr2);
 
 	/* Do not access reserved register for i.MX6UL */
-	if (!is_mx6ul()) {
+	if (!is_mx6ul() && !is_mx6ull()) {
 		/* clear MIB RAM */
 		for (i = mib_ptr; i <= mib_ptr + 0xfc; i += 4)
 			writel(0, i);