ixgbe: added Rx/Tx ring disable/enable functions

Add functions for Rx/Tx ring enable/disable. Instead of resetting the
whole device, only the affected ring is disabled or enabled.

This plumbing is used in later commits, when zero-copy AF_XDP support
is introduced.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Tested-by: William Tu <u9012063@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>