MFC: r226154, r226165

MFC: r226154, r226165

- Follow the lead of dcphy(4) and pnphy(4) and move the reminder of the PHY
  drivers that only ever attach to a particular MAC driver, i.e. inphy(4),
  ruephy(4) and xlphy(4), to the directory where the respective MAC driver
  lives and only compile it into the kernel when the latter is also there,
  also removing it from miibus.ko and moving it into the module of the
  respective MAC driver.
- While at it, rename exphy.c, which comes from NetBSD where the MAC driver
  it corresponds to also is named ex(4) instead of xl(4) but that in FreeBSD
  actually identifies itself as xlphy(4), and its function names accordingly
  for consistency.
- Additionally while at it, fix some minor style issues like whitespace
  in the register headers and add multi-inclusion protection to inphyreg.h.

Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/stable/9@227229 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f