MFC r227431-227432,227505,227509:

MFC r227431-227432,227505,227509:
r227431:
  style.
  No functional changes.

r227432:
  Remove dead ifdef.  Driver should always check raised interrupt is
  for the device.

r227505:
  It's bad idea to allocate large memory, 4KB, from stack.
  Pre-allocate the memory in device attach time. While I'm here
  remove unnecessary reassignment of error variable as it was already
  initialized. Also added a missing driver lock in TIIOCSETTRACE
  handler.

r227509:
  Export sysctl node for various interrupt moderation parameters and
  have administrators control them.  ti(4) provides a character
  device to control various other features of driver via ioctls but
  users had to write their own code to manipulate these parameters.
  It seems some default values for these parameters are not optimal
  on today's system but leave it as it was and let administrators
  change them.  The following parameters could be changed:

  dev.ti.%d.rx_coal_ticks
  dev.ti.%d.rx_max_coal_bds
  dev.ti.%d.tx_coal_ticks
  dev.ti.%d.tx_max_coal_bds
  dev.ti.%d.tx_buf_ratio
  dev.ti.%d.stat_ticks

  The interface has to be brought down and up again before a change
  takes effect.

  ti(4) controller supports hardware MAC counters with additional
  DMA statistics.  So it's doable to export these counters via
  sysctl interface.  Unfortunately, these counters are cumulative
  such that driver have to either send an explicit clear command to
  controller after extracting them or have to maintain internal
  counters to get actual changes.  Neither look good to me so
  counters were not exported via sysctl.

git-svn-id: svn://svn.freebsd.org/base/stable/8@229439 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f