cnic : Cleanup CONFIG_IPV6 & VLAN check

The cnic module needs to ensure that if ipv6 support is compiled as a module,
then the cnic module cannot be compiled as built-in as it depends on ipv6.
Made this check cleaner via Kconfig

Use simpler IS_ENABLED for CONFIG_VLAN_8021Q check

Signed-off-by: Anish Bhatt <anish@chelsio.com>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
index 7dcfb19..d8d07a8 100644
--- a/drivers/net/ethernet/broadcom/Kconfig
+++ b/drivers/net/ethernet/broadcom/Kconfig
@@ -84,7 +84,7 @@
 
 config CNIC
 	tristate "QLogic CNIC support"
-	depends on PCI
+	depends on PCI && (IPV6 || IPV6=n)
 	select BNX2
 	select UIO
 	---help---