memory: Fix adjust_endianness()

Commit a621f38de85598a13d8d8524d1a94fc6a1818215 (Direct dispatch
through MemoryRegion) moved byte swaps to a central function.

Add a missing break, so that long-sized byte swaps don't abort.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Avi Kivity <avi@redhat.com>

memory.c

@@ -942,6 +942,7 @@ static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
             break;
         case 4:
             *data = bswap32(*data);
+            break;
         default:
             abort();
         }