commit 887a9730 upstream.

ext4_expand_extra_isize() should clear only space between old and new
size.

Fixes: 6dd4ee7c # v2.6.23
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>