include/uapi/linux/openvswitch.h: use __u32 from linux/types.h

Kernel uapi header are supposed to use them. Fixes userspace compile error:

linux/openvswitch.h:583:2: error: unknown type name ‘uint32_t’
Signed-off-by: Mikko Rapeli <mikko.rapeli@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/openvswitch.h

@@ -583,7 +583,7 @@ enum ovs_userspace_attr {
 #define OVS_USERSPACE_ATTR_MAX (__OVS_USERSPACE_ATTR_MAX - 1)
 
 struct ovs_action_trunc {
-	uint32_t max_len; /* Max packet size in bytes. */
+	__u32 max_len; /* Max packet size in bytes. */
 };
 
 /**