Add lightfield example back to cmake list

Added back the lightfield example test, which was missing while
migrating tests to cmake list.

Change-Id: Ia67283226395bec14f3ffb7b63adf4be835f9c65
diff --git a/docs.cmake b/docs.cmake
index a35016e..4373c7f 100644
--- a/docs.cmake
+++ b/docs.cmake
@@ -89,6 +89,22 @@
       "Set encoder reference frame.")
 endif()
 
+if(CONFIG_AV1_ENCODER)
+  set(AOM_DOXYGEN_EXAMPLE_SOURCES ${AOM_DOXYGEN_EXAMPLE_SOURCES}
+      "${AOM_ROOT}/examples/lightfield_encoder.c")
+
+  set(AOM_DOXYGEN_EXAMPLE_DESCRIPTIONS ${AOM_DOXYGEN_EXAMPLE_DESCRIPTIONS}
+      "Lightfield encoder example.")
+endif()
+
+if(CONFIG_AV1_DECODER)
+  set(AOM_DOXYGEN_EXAMPLE_SOURCES ${AOM_DOXYGEN_EXAMPLE_SOURCES}
+      "${AOM_ROOT}/examples/lightfield_decoder.c")
+
+  set(AOM_DOXYGEN_EXAMPLE_DESCRIPTIONS ${AOM_DOXYGEN_EXAMPLE_DESCRIPTIONS}
+      "Lightfield decoder example.")
+endif()
+
 # Iterates over list named by $list_name and appends each item to $AOM_DOXYFILE
 # as values assigned to $var_name with no line breaks between list items.
 # Appends a new line after the entire config variable is expanded.