dump: qemunotes aren't commonly needed

dump: qemunotes aren't commonly needed

Only one of three architectures implementing qmp-dump-guest-memory write
qemu notes. And, another architecture (arm/aarch64) is coming, which
won't use them either. Make the common implementation truly common.

(No functional change.)

Signed-off-by: Andrew Jones <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Message-id: 1452542185[email protected]
Signed-off-by: Peter Maydell <[email protected]>