logalloc: change sprint() of a pointer to use void* explicitly
logalloc: change sprint() of a pointer to use void* explicitly

Otherwise, fmtlib dislikes it.

scylladb/scylla,scylladb/scylla,raphaelsc/scylla,raphaelsc/scylla,duarten/scylla,duarten/scylla,kjniemi/scylla,kjniemi/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,kjniemi/scylla,raphaelsc/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla