i40e: include i40e in kernel proper

This patch adds the changes for Kconfig, i40e.txt, MAINTAINERS, Kbuild
and new i40e/Makefile to build i40e with the kernel.

New driver build option is CONFIG_I40E

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
CC: PJ Waskiewicz <peter.p.waskiewicz.jr@intel.com>
CC: e1000-devel@lists.sourceforge.net
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/Makefile

@@ -9,4 +9,5 @@ obj-$(CONFIG_IGB) += igb/
 obj-$(CONFIG_IGBVF) += igbvf/
 obj-$(CONFIG_IXGBE) += ixgbe/
 obj-$(CONFIG_IXGBEVF) += ixgbevf/
+obj-$(CONFIG_I40E) += i40e/
 obj-$(CONFIG_IXGB) += ixgb/