cxgb4: increase serial number length

Some boards have longer serial numbers in their VPD, up to 24 bytes.
Signed-off-by: NDimitris Michailidis <dm@chelsio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/cxgb4/cxgb4.h

@@ -53,7 +53,7 @@
 
 enum {
 	MAX_NPORTS = 4,     /* max # of ports */
-	SERNUM_LEN = 16,    /* Serial # length */
+	SERNUM_LEN = 24,    /* Serial # length */
 	EC_LEN     = 16,    /* E/C length */
 	ID_LEN     = 16,    /* ID length */
 };