wlan - use wlan_global_serializer as if serializer

This fixes problems on SMP system using ath(4).

suggested-by: Sepherosa Ziehau <sepherosa@gmail.com>
iwn - don't acquire wlan_global_serializer in iwn_start()

With abc2d9274 iwn_start() is called with wlan_global_serializer
held already.
wlan - wlan_assert_serialized in ieee80211_init/_start/_ioctl
ath - wlan_assert_serialized in ath_init/_start/_ioctl
iwn - wlan_assert_serialized in iwn_init/_start/_ioctl
merge
merge
Merge branch 'master' of git://git.dragonflybsd.org/dragonfly into wlan_serialize
ral: release wlan serializer while loading firmware
Merge branch 'master' of git://git.dragonflybsd.org/dragonfly into wlan_serialize
vkernel - Add debugging

* Provide more information when interrupting to the db> prompt.
kernel - Cleanup SWB_NPAGES

* Remove the conditional for the SWB_NPAGES #define so the swblock
  structure remains consistent.  Remove the override in swap_pager.c.

* Previous code was confusing, but harmless.

Reported-by: Enjolras
bnx: Remove remainder of BCM5906
bnx: Defer interrupt allocation until chip reset is done
bnx: It does not make sense to have ret-ring size larger than prod-ring
bnx: Regroup TX related fields into TX ring struct
bnx: NIC based TX rings are only applicable to chips before 5705
libc: Add a few missing xdr functions

Obtained-from: FreeBSD
re: Disable IP header checksum offloading on 8168C/8168CP

These chips will generate wrong IP header checksum if IP options exist.

Obtained-from: FreeBSD
bnx: Turn softc SHORTDMA flag into per TX ring flag

Avoid extra softc accessing during transmission.