tests: Convert 'total' to double instead of float

Now that total is long casting to float may cause precision loss.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
pci: Remove unused 'Driver' forward declaration

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>