reiserfs: remove unused iter variable

clang with W=1 reports
fs/reiserfs/stree.c:1265:6: error: variable
  'iter' set but not used [-Werror,-Wunused-but-set-variable]
        int iter = 0;
            ^
This variable is not used so remove it.

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230331120325.1855111-1-trix@redhat.com>