ibmvnic: Remove skb->protocol checks in ibmvnic_xmit

Having these checks in ibmvnic_xmit causes problems with VLAN
tagging and balance-alb/tlb bonding modes. The restriction they
imposed can be removed.

Signed-off-by: John Allen <jallen@linux.vnet.ibm.com>
Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>