bpf: add missing C++ guards

Some public header files were missing 'extern "C"' C++ guards,
and couldn't be used by C++ applications. Add the missing guards.

Fixes: 7a33572057 ("lib: remove C++ include guard from private headers")
Cc: stable@dpdk.org

Signed-off-by: Brian Dooley <brian.dooley@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

lib/bpf/bpf_def.h

@@ -7,6 +7,10 @@
 #ifndef _RTE_BPF_DEF_H_
 #define _RTE_BPF_DEF_H_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @file
  *
@@ -140,4 +144,8 @@ struct ebpf_insn {
  */
 #define	EBPF_FUNC_MAX_ARGS	(EBPF_REG_6 - EBPF_REG_1)
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* RTE_BPF_DEF_H_ */