bdwgc: fix compile for sparc

We need to use a patch from master git.
https://github.com/ivmai/bdwgc/commit/e2bf29b7801357c1ad28c2948a3f88c655dd722a

Fixes following autobuilder failures:
http://autobuild.buildroot.net/results/220b3d49b8ad891e5dd3aae759319100a1500701/
http://autobuild.buildroot.net/results/b7465d175f03c9461693a92885028723772c7814/



Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>