qom: Fix warning from Sparse

Sparse report:

qom/cpu.c:99:5: warning: returning void-valued expression

Cc: Andreas Färber <afaerber@suse.de>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/qom/cpu.c b/qom/cpu.c
index 970377e..108bfa2 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -96,7 +96,7 @@
 {
     CPUClass *cc = CPU_GET_CLASS(cpu);
 
-    return cc->get_memory_mapping(cpu, list, errp);
+    cc->get_memory_mapping(cpu, list, errp);
 }
 
 static void cpu_common_get_memory_mapping(CPUState *cpu,