Panic with a clear message if the viona API is too old

[citrus-it]

Currently if one runs propolis on a system which does not have a new
enough viona API, a stacktrace like this is generated.

failed to enable promisc mode on vnic0: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }
called `Result::unwrap()` on an `Err` value: Os { code: 25, kind: Uncategorized, message: "Inappropriate ioctl for device" }
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: propolis::hw::virtio::viona::PciVirtioViona::new_with_queue_sizes
   4: propolis::hw::virtio::viona::PciVirtioViona::new

Since we don't currently support anything older than the V6 API in
propolis we should at least produce a useful error message to the
operator. It would be possible to fall back to the older API if we
wish to implement that.