iproute2: fix the configure process

iproute2: fix the configure process

Previously, the iproute2's configure script is actually run in the
do_compile stage. There's a Makefile rule 'all: Config' which makes
the configure process run to generate the Config file.

However, this makes it hard to fix the dependency problems. We need
to generate the Config file in the do_configure stage.

Add do_configure_append to separate the configure process from the
compile process.

Besides, explicitly disable ATM support for iproute2, otherwise we'll
sometimes meet errors like below when building.

  ld: cannot find -latm
  collect2: error: ld returned 1 exit status
  Makefile:154: recipe for target 'q_atm.so' failed
  make[1]: *** [q_atm.so] Error 1

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>