elfutils: check data_list.data.d.d_buf before free it

elfutils: check data_list.data.d.d_buf before free it

[YOCTO #12791]

The one which actually saves the data is data_list.data.d.d_buf, so check it
before free rawdata_base.

This can fix a segmentation fault when prelink libqb_1.0.3:
prelink: /usr/lib/libqb.so.0.18.2: Symbol section index outside of section numbers

The segmentation fault happens when prelink call elf_end().

Fixed:
MACHINE="qemux86-64"
IMAGE_INSTALL_append = " libqb" #libqp is from meta-openembedded
$ bitbake core-image-minimal
Segmention fault

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>