arm/nseries: Fix warnings from Sparse

Sparse report:

arm/nseries.c:1406:5: warning: returning void-valued expression
arm/nseries.c:1411:5: warning: returning void-valued expression

Cc: Andrzej Zaborowski <balrogg@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

hw/arm/nseries.c

@@ -1403,12 +1403,12 @@ static struct arm_boot_info n810_binfo = {
 
 static void n800_init(MachineState *machine)
 {
-    return n8x0_init(machine, &n800_binfo, 800);
+    n8x0_init(machine, &n800_binfo, 800);
 }
 
 static void n810_init(MachineState *machine)
 {
-    return n8x0_init(machine, &n810_binfo, 810);
+    n8x0_init(machine, &n810_binfo, 810);
 }
 
 static QEMUMachine n800_machine = {