MFC r257154:

Merging local and remote bitmaps must be protected by hr_amp lock.

This is believed to fix hastd crashes, which might occur during
synchronization, triggered by the failed assertion:

 Assertion failed: (amp->am_memtab[ext] > 0),
 function activemap_write_complete, file activemap.c, line 351.
MFC r257307:
  Fix regression introduced in r235816.
  r235816 triggered kernel panic or hang after warm boot.
  Don't blindly restore BCE_EMAC_MODE media configuration in
  bce_reset().  If driver is about to shutdown it will invoke
  bce_reset() which in turn results in restoring BCE_EMAC_MODE
  media configuration.  This operation seems to confuse controller
  firmware.