i40e: Setting queue count to 1 using ethtool is valid

Fix a bug where ethtool set-channels would return failure when configuring
only one Rx queue.

Change-ID: Id833c48c17d71e352b30f3249f6acf9e7aaec57e
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>