While ../zfs/libzfs.h mostly works, there are a few situations where
it does not. Eliminate the problem by using plain libzfs.h, like we do
for ufs support. This fixes the weird cases, and is easier to
understand. It also follows the general style convetion of avoiding
../ in #includes.
There's no reason to have multiple copies of lszfs and
reloadbe. Consolidate them into one location. Also ldi_get_size is the
same everywhere (except sparc64). Make it the same everywhere as the
common definition is more general and will work on spar64.