Fix various places which cast a pointer to a uint64_t or vice versa.

[jhb]

Summary

GCC warns about the mismatched sizes on 32-bit platforms.

[imp]

sys/dev/iser/iser_initiator.c

293

Dropping the extra cast may lead to warnings when sizeof(uintptr_t) != sizeof(size_t)

[imp]

sys/dev/iser/iser_initiator.c

293

I tried to delete this comment, since it turned out to be wrong.

[jhb]

sys/dev/iser/iser_initiator.c

293

Only CHERI has those and it's actually more well-defined to add offsets (size_t or ptrdiff_t) to pointers than to add two pointers together.