elf: Fix failure handling in _dl_map_object_from_fd

The failure paths in _dl_map_object_from_fd did not clean every
potentially allocated resource up.

Handle l_phdr, l_libname and mapped segments in the common failure
handling code.

There are various bits that may not be cleaned properly on failure
(e.g. executable stack, incomplete dl_map_segments) fixing those
need further changes.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>