Bug#1101533: pytorch-geometric: Failing autopkgtests

[Santiago Vila]

Hi.

I finally found the way to disable the autopkgtests on riscv64, where
they still fail. Now there is a real chance to see the package in
testing after some days.

I've also fixed a few more things, everything documented in salsa.

I did not really plan to make so many uploads for this package, as my
initial aim was just to fix the build on single-cpu systems, but as
it's often said: one thing leads to another.

After all these changes, I expect not to touch the package anymore in
the near future.

Thanks.