MFC r277454, r277460, r277465, r277466, r277467, r277469, r277470, r277471,

MFC r277454, r277460, r277465, r277466, r277467, r277469, r277470, r277471,
    r277472, r277473, r277474, r277475, r277476, r277477, r277478, r277479,
    r277480, r277512, r277516:

  Add inline implementations of arm bus_space_read/write_N().

  Revise the arm bus_space implementation to avoid dereferencing the tag on
  every operation to retrieve the bs_cookie value almost nothing actually uses.

  Use the explicit member initializer style to init the bus_space struct.

  Use arm/bus_space-v6.c for all armv6 systems

  Consolidate many identical implementations of bus_space to a single
  common tag and implementation shared by armv4 and armv6.

  Micro-optimize the new arm inline bus_space implementation by grouping all
  the data the inline functions access together at the start of the bus_space
  struct so that they all fit in a single cache line.

git-svn-id: svn://svn.freebsd.org/base/stable/10@278727 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f