dump: Fix HMP dump-guest-memory -z without -R

-z without -R has no effect: the dump format remains @elf.  Fix the
logic error so it becomes @kdump-zlib.

Fixes: e6549197f7ed (dump: Add command interface for kdump-raw formats)
Fixes: CID 1523841
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

dump/dump-hmp-cmds.c

@@ -41,7 +41,7 @@ void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict)
         dump_format = DUMP_GUEST_MEMORY_FORMAT_WIN_DMP;
     }
 
-    if (zlib && raw) {
+    if (zlib) {
         if (raw) {
             dump_format = DUMP_GUEST_MEMORY_FORMAT_KDUMP_RAW_ZLIB;
         } else {