i40e: rename 'change' variable to 'autoneg_changed'

This variable isn't actually very descriptive and makes the code a bit
confusing as to what it is being used for.  This patch enhances the
variable with the longer name, 'autoneg_changed', which makes it clear
we are concerned with autoneg changing in this context.

Signed-off-by: Alan Brady <alan.brady@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>