netif/dc issues

[Eduardo Tongson <propolice@xxxxxxxxx>]

On -Preview and HEAD
my Davicom 9102 10/100 cards 
are choking out these messages

. ..
mfree: m->m_nextpkt != NULL
Trace beginning at frame (0xdeadbeef) 
m_free (..) at m_free+0x5e
m_free (..) at m_free+0x5e
m_freem (..) at m_freem+0x2e
dc_start (..) at dc_start+0xd4
dc_tick (...) at dc_tick+0x148
softclock_handler (...) at softclock_handler+0xe2
lwkt_exit() lwkt_exit
. ..
If i get that while on my 2-port KVM switch it locks up the keyboard
which then needs a hard reset.

In hopes of fixing it, I brought in changes from freebsd (see submit@)
but still no luck with the updates

The card works fine on NetBSD, OpenBSD, QNX, Linux

--ed 
Eduardo Tongson