Constify two structs.
Correct some typos.

Compile-tested and run-tested (module inserted) on 2.6.18-rc4-mm3.

Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>