datapath: Add 32-bit compatibility ioctls.

datapath: Add 32-bit compatibility ioctls.

When a 32-bit userspace program runs on a 64-bit kernel, data structures
that contain members whose sizes or alignments change from 32- to 64-bit
must be translated when they are passed to ioctls.  This commit adds such
support for openvswitch_mod.

We should really reconsider some parts of the Open vSwitch ioctl interface
to avoid needing as much translation as we do.

Lightly tested with 32-bit userspace on sparc64.