linux-user: add netlink CARRIER_UP_COUNT/CARRIER_DOWN_COUNT

Error is reported with libuv test suite:

 not ok 311 - udp_multicast_interface6
 # exit code 134
 # Output from process `udp_multicast_interface6`:
 # Unknown host QEMU_IFLA type: 47
 # Unknown host QEMU_IFLA type: 48
 # Unknown host QEMU_IFLA type: 47
 # Unknown host QEMU_IFLA type: 48
 # Unknown host QEMU_IFLA type: 47
 # Unknown host QEMU_IFLA type: 48
 # Unknown host QEMU_IFLA type: 47
 # Unknown host QEMU_IFLA type: 48
 # Unknown host QEMU_IFLA type: 47
 # Unknown host QEMU_IFLA type: 48

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180627212152.26525-2-laurent@vivier.eu>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2117fb1..4460f1e 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -2522,6 +2522,8 @@
     case QEMU_IFLA_NUM_VF:
     case QEMU_IFLA_GSO_MAX_SEGS:
     case QEMU_IFLA_GSO_MAX_SIZE:
+    case QEMU_IFLA_CARRIER_UP_COUNT:
+    case QEMU_IFLA_CARRIER_DOWN_COUNT:
         u32 = RTA_DATA(rtattr);
         *u32 = tswap32(*u32);
         break;