bnxt_en: Return -EOPNOTSUPP for ETHTOOL_GREGS on VFs.

Debug firmware commands are not supported on VFs to read registers.
This patch avoids logging unnecessary access_denied error on VFs
when user calls ETHTOOL_GREGS.

By returning error in get_regs_len() method on the VF, the get_regs()
method will not be called.

Fixes: b5d600b027 ("bnxt_en: Add support for 'ethtool -d'")
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c

@@ -1322,6 +1322,9 @@ static int bnxt_get_regs_len(struct net_device *dev)
 	struct bnxt *bp = netdev_priv(dev);
 	int reg_len;
 
+	if (!BNXT_PF(bp))
+		return -EOPNOTSUPP;
+
 	reg_len = BNXT_PXP_REG_LEN;
 
 	if (bp->fw_cap & BNXT_FW_CAP_PCIE_STATS_SUPPORTED)