qeth: Add new priority queueing options

The existing options for priority queueing within OSA devices were based on
the now partially defunct TOS field. This patch adds two new options as
follows:
   - prio_queueing_skb: bases priority queueing on skb-priority
   - prio_queueing_vlan: uses the priority code point in the 802.1Q header

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Reviewed-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>