e1000: add missing register defines

e1000: add missing register defines

Added defines for the EEC, SHADOWINF and FLFWUPDATE registers needed for
the nvmupd_validate_offset function to correctly validate the NVM update
offset.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Guinan Sun <guinanx.sun@intel.com>
Reviewed-by: Wei Zhao <wei.zhao1@intel.com>
Approved by:	imp
Obtained from:	DPDK (2c7fe65ab9a31e6ebf438dad7ccc59bcde83a89f)
MFC after:	1 week

(cherry picked from commit 09888d4bc1a2c45d121046f79be5c01e4889a67e)