fm10k: don't clear the RXQCTL register when enabling or disabling queues

Ensure that other bits in the RXQCTL register do not get cleared. This
ensures that bits related to queue ownership are maintained.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>