cmake: Fix VAPI .hpp generation

Change-Id: I2bec3b2511f00d017f9b3a727809631695222c1a
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
diff --git a/src/vpp-api/vapi/CMakeLists.txt b/src/vpp-api/vapi/CMakeLists.txt
index 103e7c5..0aff882 100644
--- a/src/vpp-api/vapi/CMakeLists.txt
+++ b/src/vpp-api/vapi/CMakeLists.txt
@@ -42,7 +42,7 @@
     OUTPUT ${output}
     WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
     COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/vapi_cpp_gen.py
-    ARGS --remove-path ${input}
+    ARGS --gen-h-prefix=vapi --remove-path ${input}
     DEPENDS ${input} vapi_cpp_gen.py vapi_json_parser.py
     COMMENT "Generating VAPI C++ header ${output}"
   )
diff --git a/src/vpp-api/vapi/vapi_cpp_gen.py b/src/vpp-api/vapi/vapi_cpp_gen.py
index adf85c7..3260268 100755
--- a/src/vpp-api/vapi/vapi_cpp_gen.py
+++ b/src/vpp-api/vapi/vapi_cpp_gen.py
@@ -136,7 +136,7 @@
     print("#define %s" % include_guard)
     print("")
     print("#include <vapi/vapi.hpp>")
-    print("#include <%s%s>" % (gen_h_prefix, json_to_c_header_name(j)))
+    print("#include <%s%s>" % (gen_h_prefix, json_to_c_header_name(f)))
     print("")
     print("namespace vapi {")
     print("")