Revert r269093 which introduced physical zio alignment transform

Size of physical ZIOs must never be implicitly adjusted, it's
a responsibility of a caller to make sure that such a ZIO has proper offset
and size.

Discussed with:	delphij, gibbs
MFC after:	2 weeks


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274627 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f