package/bdwgc: musl build failure

Fixes http://autobuild.buildroot.net/results/1ed/1edb5e7dab88d3fefca533ab56f7ddc7dd5411d2/



Upstream removed unused code which was causing musl compilation issues.

Signed-off-by: Brendan Heading <brendanheading@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>