package/bdwgc: only enable on supported architectures

package/bdwgc: only enable on supported architectures

bdwgc has support for a sub-set of the architectures we support.

Since there is roughly a 50-50 split of our architectures that have
support in bdwgc vs. those that do not, use a positive dependency logic,
rather than a negative one.

The list was constructed by visual inspection of the source code of
bdwgc, but the header doing the check is, to say it politely, a bit
difficult to read...

So, some working archotectures may be missing. Users needing it may
investigate if their architectures are indeed supported.

Fixes;
    http://autobuild.buildroot.net/results/529/529b0b6dd47744c13f56e59a4c669a3f5d56530d/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Pedro Aguilar <paguilar@paguilar.org>
Cc: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>