gcc: bump elfutils version to 0.156

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
elfutils: remove dead patches

The patches were intended for elfutils 0.155 and are already included
into 0.156.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>