dm ioctl: refactor dm_table_complete

This change unifies the various checks and finalization that occurs on a
table prior to use.  By doing so, it allows table construction without
traversing the dm-ioctl interface.

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --cc drivers/md/dm-ioctl.c
Simple merge

diff --cc drivers/md/dm-table.c
Simple merge

diff --cc drivers/md/dm.h
Simple merge