drivers: net: ethernet: octeon_mgmt: fix a compiler warning

Fix the following compiler warning:

drivers/net/ethernet/octeon/octeon_mgmt.c: In function 'octeon_mgmt_clean_tx_buffers':
drivers/net/ethernet/octeon/octeon_mgmt.c:295:4: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
    u64 ns = cvmx_read_csr(CVMX_MIXX_TSTAMP(p->port));
    ^

Signed-off-by: Aaro Koskinen <aaro.koskinen@nsn.com>
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/octeon/octeon_mgmt.c

@@ -290,9 +290,11 @@ static void octeon_mgmt_clean_tx_buffers(struct octeon_mgmt *p)
 		/* Read the hardware TX timestamp if one was recorded */
 		if (unlikely(re.s.tstamp)) {
 			struct skb_shared_hwtstamps ts;
+			u64 ns;
+
 			memset(&ts, 0, sizeof(ts));
 			/* Read the timestamp */
-			u64 ns = cvmx_read_csr(CVMX_MIXX_TSTAMP(p->port));
+			ns = cvmx_read_csr(CVMX_MIXX_TSTAMP(p->port));
 			/* Remove the timestamp from the FIFO */
 			cvmx_write_csr(CVMX_MIXX_TSCTL(p->port), 0);
 			/* Tell the kernel about the timestamp */