ixgbe: Fill out PCIe speed and width enums with values

This patch fills in the values for bus speed and width of the
ixgbe_bus_speed and ixgbe_bus_width enums.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>