MAINTAINERS: Update MAINTAINERS for Intel ethernet drivers

Add Jesse Brandeburg and myself; remove Jeff Kirsher.

CC: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
CC: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>