Prevent sign extension due to pointer arithmetics
Prevent sign extension due to pointer arithmetics

This should make mpii(4) work on i386 again, apparently.
Problem identified and a slightly different fix proposed
by Christiano F. Haesbaert and Pedro Martelletto of Bitrig.
Huge thanks for tracking this down, guys!

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars