opkg 0.1.8: remove it since it doesn't work

opkg 0.1.8: remove it since it doesn't work

Remove opkg_0.1.8.bb and the related files since it doesn't work:

- It doesn't support the "--force_postinstall" option which is used by
  package_ipk.bbclass.

- It still doesn't work after remove the "--force_postinstall" option,
  it can't install the packages in complementary_pkgs.txt.

[YOCTO #3136]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>