Fix for kern/152853, pullup in the wrong
	place in em_xmit causes UDP failure. Thanks
	to Petr Lampa for the patch.

Approved by: re (bz)

	- Pieces of the failure path in em_xmit got deleted along
	  the way, correct this.
	- local_timer had a leftover TX_UNLOCK without matching
	  LOCK in the error path, remove it.

Approved by:  re (bz)

Remove the test for a minimum frame size from the IPV6 TX context
descriptor setup, when using VLANs and HW TAGGING the length of
an ICMP6 frame will fail this test and be discarded.

Approved by: re

Correct the RX discard and refresh_mbuf logic to match igb, the old
discard code could cause panics due to a bad pointer, now simply
have discard always free mbufs and depend on refresh. In the refresh
code, make sure the mbuf and soft buf struct are properly reset.

Approved by: re

  Do not allocate multicast array memory in multicast filter
  configuration function. For failed memory allocations, em(4)/lem(4)
  called panic(9) which is not acceptable on production box.
  igb(4)/ixgb(4)/ix(4) allocated the required memory in stack which
  consumed 768 bytes of stack memory which looks too big.

  To address these issues, allocate multicast array memory in device
  attach time and make multicast configuration success under any
  conditions. This change also removes the excessive use of memory in
  stack.

  Reviewed by:	jfv

  If em(4) failed to allocate RX buffers, do not call panic(9).
  Just showing some buffer allocation error is more appropriate
  action for drivers. This should fix occasional panic reported on
  em(4) when driver encountered resource shortage.

  Reviewed by:	jfv

  Do not call voluntary panic(9) in case of if_alloc() failure.

  Reviewed by:	jfv

  Make sure not to access unallocated stats memory.

  Reviewed by:	jfv

Tweak the stats exported by the e1000 drivers:
- Add a single sysctl procedure to all three drivers to read an arbitrary
  register (the register is passed as arg2).  Use it to replace existing
  routines in igb(4) that used a separate routine for each register, and
  to add support for missing stats in em(4) and lem(4).
- Move the 'rx_overruns' and 'watchdog_timeouts' stats out of the MAC stats
  section as they are driver stats, not MAC counters.
- Simplify the code that creates per-queue stats in igb(4) to use a single
  loop and remove duplicated code.
- Properly read all 64 bits of the 'good octets received/transmitted' in
  em(4) and lem(4).
- Actually read the interrupt count registers in em(4), and drop the
  'host to card' sysctl stats from em(4) as they are not implemented in
  any of the hardware this driver supports.
- Restore several stats to em(4) that were lost in the earlier stats
  conversion including per-queue stats.
- Export several MAC stats in em(4) that were exported in igb(4) but not
  in em(4).
- Export stats in lem(4) using individual sysctls as in em(4) and igb(4).