ppc/pef.c: initialize cgs->ready in kvmppc_svm_init()

QEMU is failing to launch a CGS pSeries guest in a host that has PEF
support:

qemu-system-ppc64: ../softmmu/vl.c:2585: qemu_machine_creation_done: Assertion `machine->cgs->ready' failed.
Aborted

This is happening because we're not setting the cgs->ready flag that is
asserted in qemu_machine_creation_done() during machine start.

cgs->ready is set in s390_pv_kvm_init() and sev_kvm_init(). Let's set it
in kvmppc_svm_init() as well.

Reported-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210528201619.52363-1-danielhb413@gmail.com>
Acked-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/pef.c

@@ -41,7 +41,7 @@ struct PefGuest {
     ConfidentialGuestSupport parent_obj;
 };
 
-static int kvmppc_svm_init(Error **errp)
+static int kvmppc_svm_init(ConfidentialGuestSupport *cgs, Error **errp)
 {
 #ifdef CONFIG_KVM
     static Error *pef_mig_blocker;
@@ -65,6 +65,8 @@ static int kvmppc_svm_init(Error **errp)
     /* NB: This can fail if --only-migratable is used */
     migrate_add_blocker(pef_mig_blocker, &error_fatal);
 
+    cgs->ready = true;
+
     return 0;
 #else
     g_assert_not_reached();
@@ -102,7 +104,7 @@ int pef_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
         return -1;
     }
 
-    return kvmppc_svm_init(errp);
+    return kvmppc_svm_init(cgs, errp);
 }
 
 int pef_kvm_reset(ConfidentialGuestSupport *cgs, Error **errp)