gve: Fix swapped vars when fetching max queues

[ Upstream commit 1db1a862a08f85edc36aad091236ac9b818e949e ]

Fixes: 893ce44d ("gve: Add basic driver framework for Compute Engine Virtual NIC")
Signed-off-by: Bailey Forrest <bcf@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>