Errors in 5-6 upgrade path

ip2cc_update_6001() tries to change a field definition, but ip2cc_update_6002() drops the same table if it exists. On my Drupal 5 install, it doesn't, so this causes an MySQL error. Since we're dropping the table anyway, I just removed that hunk from the previous update.

Also a note that _6002() should really be using db_drop_table() instead of update_sql()