Fix build on non-linux platforms after another VIR_AUTOPTR patches

Caused by commit f7d0663d. The problem is missing libnl library on
these platforms, so the VIR_DEFINE_AUTOPTR_FUNC has to be compiled in
conditionally.
Signed-off-by: NErik Skultety <eskultet@redhat.com>

src/util/virnetlink.h

@@ -36,6 +36,9 @@
 #   undef inline
 #  endif
 
+typedef struct nl_msg virNetlinkMsg;
+VIR_DEFINE_AUTOPTR_FUNC(virNetlinkMsg, nlmsg_free)
+
 # else
 
 struct nl_msg;
@@ -45,8 +48,6 @@ struct nlmsghdr;
 
 # endif /* __linux__ */
 
-typedef struct nl_msg virNetlinkMsg;
-
 int virNetlinkStartup(void);
 void virNetlinkShutdown(void);
 
@@ -126,6 +127,4 @@ int virNetlinkEventAddClient(virNetlinkEventHandleCallback handleCB,
 int virNetlinkEventRemoveClient(int watch, const virMacAddr *macaddr,
                                 unsigned int protocol);
 
-VIR_DEFINE_AUTOPTR_FUNC(virNetlinkMsg, nlmsg_free)
-
 #endif /* __VIR_NETLINK_H__ */