reiserfs: Make reiserfs_xattr_handlers static

Silences the following sparse warning: fs/reiserfs/xattr.c:899:28: warning:
symbol 'reiserfs_xattr_handlers' was not declared. Should it be static?

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>