print.c: improve device printing.

Add headers and columns (i.e. print device entries in a table-like manner).
Also, add and use test_state_to_text() to support the new test states.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

git-svn-id: svn://flashrom.org/flashrom/trunk@1807 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1