igb: Change version to remove number after -k in kernel versions.

This patch changes the way versioning is done for igb in the kernel by
removing the number after the "k."  It has been determined that just the
"k" is sufficient to identify a kernel version and the following number
was used in an inconsistent manner.

Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>