nvme: Fix sync controller reset return

If a controller reset is requested while the device has no namespaces,
we were incorrectly returning ENETRESET. This patch adds the check for
ADMIN_ONLY controller state to indicate a successful reset.

Fixes: 8000d1fd

  ("nvme-rdma: fix sysfs invoked reset_ctrl error flow ")
Cc: <stable@vger.kernel.org>
Signed-off-by: Charles Machalow <charles.machalow@intel.com>
[changelog]
Signed-off-by: Keith Busch <keith.busch@intel.com>