Fix handling of write protection at register space address +2.

Since r1833 we added the offset of the virtual register in several
functions, which produced segfaults. This patch renames a few
parameters and reorganizes/fixes various parts of the
changelock_regspace2_block() function - hence the rather big diff.

Thanks to Roman Lebedev for reporting this issue and testing numerous
revisions of this patch.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>

git-svn-id: svn://flashrom.org/flashrom/trunk@1859 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1