virtio-gpu-3d: add support for second capability set (v4)

Due to a kernel bug we can never increase the size of capability
set 1, so introduce a new capability set in parallel, old userspace
will continue to use the old set, new userspace will start using
the new one when it detects a fixed kernel.

v2: don't use a define from virglrenderer, just probe it.
v3: fix compilation when virglrenderer disabled
v4: fix style warning, just use ?: op instead.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Message-id: 20180223023814.24459-1-airlied@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>