bnx2x: Prevent false warning for lack of FC NPIV

Not all adapters have FC-NPIV configured. If bnx2fc is used with such an
adapter, driver would read irrelevant data from the the nvram and log
"FC-NPIV table with bad length..." In system logs.

Simply accept that reading '0' as the feature offset in nvram indicates
the feature isn't there and return.
Reported-by: NAndrew Patterson <andrew.patterson@hpe.com>
Signed-off-by: NYuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c

@@ -14885,6 +14885,10 @@ static int bnx2x_get_fc_npiv(struct net_device *dev,
 	}
 
 	offset = SHMEM2_RD(bp, fc_npiv_nvram_tbl_addr[BP_PORT(bp)]);
+	if (!offset) {
+		DP(BNX2X_MSG_MCP, "No FC-NPIV in NVRAM\n");
+		goto out;
+	}
 	DP(BNX2X_MSG_MCP, "Offset of FC-NPIV in NVRAM: %08x\n", offset);
 
 	/* Read the table contents from nvram */