MFC: r228022, r228026

MFC: r228022, r228026

For sparc64 also adjust the geometry of da(4) driven disks to not overflow
the 16-bit cylinders field of the VTOC8 disk label (at around 502GB). The
geometry chosen for disks above that limit allows to use disks up to 2TB,
which is the limit of the extended VTOC8 format. The geometry used for
disks smaller than the 16-bit cylinders limit stays the same as used by
cam_calc_geometry(9) for extended translation.
Thanks to Hans-Joerg Sirtl for providing hardware for testing this change.

git-svn-id: svn://svn.freebsd.org/base/stable/8@230666 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f