Pass the memory file descriptor and offset when registering ram

Since the memory file descriptor is the canonical reference to guest
memory, pass that and the offset when registering guest memory.
Future fd-based kvm proposals might even not require a userspace
address [*].

No functional change intended.

Signed-off-by: Fuad Tabba <tabba@google.com>

[*] https://lore.kernel.org/all/20221025151344.3784230-1-chao.p.peng@linux.intel.com/
11 files changed