virtio: add support for 64 bit features.

virtio: add support for 64 bit features.

Change u32 to u64, and use BIT_ULL and 1ULL everywhere.

Note: transports are unchanged, and only set low 32 bit.
This guarantees that no transport sets e.g. VERSION_1
by mistake without proper support.

Based on patch by Rusty.

Signed-off-by: Rusty Russell <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>