qlcnic: fix vlan TSO on big endian machine

o desc->vlan_tci is in __le16 format. Doing htons and
  cpu_to_le64 again on vlan_tci, result in invalid value on ppc.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>