qmp: Fix higher half vaddrs for [p]memsave

Fixes higher-half address parsing for QMP commands
`[p]memsave`.

Signed-off-by: Josh Junon <junon@oro.sh>
Message-ID: <20240802140704.13591-1-junon@oro.sh>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Subject tweaked, and one PRId64 updated to PRIu64]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2 files changed