nova: increase number of available cap indexes

Noux test requires some more indexes. We don't free all up because of a missing
reference counting implementation of indexes in base-nova.

Issue #394
nova: use kernel branch adjusted to Genode

Since we have now more than a handful patches to the vanilla kernel, we
better switch to a separate git repository in order to review and to maintain
the patches more effectively.

Remove the patches, they are already in the kernel branch.

Fixes #394