Sync the e1000 drivers with what's in head as of r294327, modulo parts

Sync the e1000 drivers with what's in head as of r294327, modulo parts
that don't apply to stable/10 (driver API, if_inc_counter(), RSS changes
etc.) and modulo r287465 (which reportedly breaks igb(4)), i. e. assorted
fixes and improvements only:

o MFC r267385 (partial):
  - Don't compare bus_dma map pointers for static DMA allocations against
    NULL to determine if bus_dmamap_unload() or bus_dmamem_free() should be
    called. Instead, check the associated bus and virtual addresses.
  - Don't clear static DMA maps to NULL.
o MFC r284933:
  Delete the refernce to VLAN handling being disabled by default. This is
  no longer the case. [1]
o MFC r285639:
  Add an adapter CORE lock in the DDB hook em_dump_queue to avoid WITNESS
  panic in em_init_locked() while debugging.
o MFC r285879:
  - Remove unused txd_saved.
  - Intialize txd_upper, txd_lower and txd_used at declaration.
o MFC r286162:
  Free mbufs when busdma loading fails.
o MFC r286829:
  Add capability to disable CRC stripping as it breaks IPMI/BMC capabilities
  on certain adatpers. [2]
o MFC r286831: [3]
  - Increase EM_MAX_SCATTER to 64 such that the size of em_xmit()::
    segs[EM_MAX_SCATTER] doesn't get overrun by things like NFS that can
    and do shove more than 32 segs when being used with em(4) and TSO4.
  - Update tso handling code in em_xmit() with update from jhb@
  - Set if_hw_tsomax, if_hw_tsomaxsegcount and if_hw_tsomaxsegsize to
    appropriate values.
  - Define a TSO workaround "magic" number of 4 that is used to avoid an
    alignment issue in hardware.
  - Change a couple of integer values that were used as booleans to actual
    bool types.
  - Ensure that em_enable_intr() enables the appropriate mask of interrupts
    and not just a hardcoded define of values.
o MFC r286832:
  e1000/if_lem.c bump to 1.1.0
o MFC r286833:
  Bump all copywrite dates to 2015.
o MFC r287112:
  Style/whitespace cleanup in shared/common code.
o MFC r293331:
  - Switch em(4) to the extended RX descriptor format.
  - Split rxbuffer and txbuffer apart to support the new RX descriptor
    format structures. Move rxbuffer manipulation to em_setup_rxdesc() to
    unify the new behavior changes.
  - Add a RSSKEYLEN macro for help in generating the RSSKEY data structures
    in the card.
  - Change em_receive_checksum() to process the new rxdescriptor format
    status bit.
o MFC r293332:
  Disable the reuse of checksum offload context descriptors in the case
  of multiple queues in em(4). Document errata in the code.
o MFC r293854:
  Given that em(4), lem(4) and igb(4) hardware doesn't require the
  alignment guarantees provided by m_defrag(9), use m_collapse(9)
  instead for performance reasons.
  While at it, sanitize the statistics softc members, i. e. retire
  unused ones and add SYSCTL nodes missing for actually used ones.

PR:	118693 [1], 161277 [2], 195078 [3], 199174 [3], 200221 [3]

git-svn-id: svn://svn.freebsd.org/base/stable/10@294958 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f