cpus: Improve error messages on memsave, pmemsave write error

qmp_memsave() and qmp_pmemsave() report fwrite() error as

    An IO error has occurred

Improve this to

    writing memory to '<filename>' failed

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240513141703.549874-5-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
1 file changed