e1000e: fix sparse warnings

Fix sparse warnings from e1000e driver in net-2.6.24.

Added a sparse fix for module param arrays which can have int values
but only the array index needs to be unsigned. --Auke

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>