recvd_props_mode: use a uintptr_t to stash nvlists
Avoid assuming than a uint64_t can hold a pointer.
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Signed-off-by: Brooks Davis <brooks.davis@sri.com>
Closes #14131