With it being unspecified, it'll have to fall back to Rule Zero: the GM is always right. GM decides which range your spirit's Binding power has.
As a personal take: I'd lean towards saying summoned spirits have the Touch range.
Edit: Alternately, one might say summoned spirits come with the most restrictive range: Self. Range could be upgraded to touch by selecting binding again via optional bonus power pick, and range could be upgraded again to LOS by picking it a third time.