reiserfs: fix memset byte count during resize

Correct the memset in reiserfs_resize to clear the memory allocated for the
new bitmap info structs.  Previously, it would clear the memory used by the
old size.  Depending on the contents of memory, this could cause incorrect
caching behavior for bitmap blocks in the newly allocated area.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>