The node suspend capabilities APIs should not have been put into
util.[ch]. Instead move them into virnodesuspend.[ch]

* src/util/util.c, src/util/util.h: Remove suspend capabilities APIs
* src/util/virnodesuspend.c, src/util/virnodesuspend.h: Add
  suspend capabilities APIs
* src/qemu/qemu_capabilities.c: Include virnodesuspend.h