i40e/i40evf: grab NVM devstarter version not image version

0x2A is the NVM version so it has useful data but it is per image
version every image can have a different one. 0x18 is the dev starter
version which all the images for release will have the same version.
Of the two 0x18 is more useful and is what should be displayed.

Change-ID: Idf493da13a42ab211e2de0bef287f5de51033cca
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>