[Tizen/API] Use function instead of API in documentation

API review scripts recommands to use the word 'function' instead of
'API' in documentation as below. So this patch fixes this issue.

Are you sure "API" in this case shouldn't be "function"? If this
sentence refers to a single function, not a set of functions, it should
be "function".

Signed-off-by: Sangjung Woo <sangjung.woo@samsung.com>

Author: again4you

tizen-api/doc/nnstreamer_doc.h

@@ -45,28 +45,28 @@
  *
  * @defgroup CAPI_ML_NNSTREAMER_PIPELINE_MODULE NNStreamer Pipeline
  * @ingroup  CAPI_ML_NNSTREAMER
- * @brief The NNStreamer API provides interfaces to create and execute stream pipelines with neural networks and sensors.
+ * @brief The NNStreamer function provides interfaces to create and execute stream pipelines with neural networks and sensors.
  * @section CAPI_ML_NNSTREAMER_PIPELINE_HEADER Required Header
  *   \#include <nnstreamer/nnstreamer.h> \n
  *
  * @section CAPI_ML_NNSTREAMER_PIPELINE_OVERVIEW Overview
- * The NNStreamer API provides interfaces to create and execute stream pipelines with neural networks and sensors.
+ * The NNStreamer function provides interfaces to create and execute stream pipelines with neural networks and sensors.
  *
- *  This API allows the following operations with NNStreamer:
+ *  This function allows the following operations with NNStreamer:
  * - Create a stream pipeline with NNStreamer plugins, GStreamer plugins, and sensor/camera/mic inputs
  * - Interfaces to push data to the pipeline from the application
  * - Interfaces to pull data from the pipeline to the application
  * - Interfaces to start/stop/destroy the pipeline
  * - Interfaces to control switches and valves in the pipeline.
  *
- *  Note that this API set is supposed to be thread-safe.
+ *  Note that this function set is supposed to be thread-safe.
  *
  * @section CAPI_ML_NNSTREAMER_PIPELINE_FEATURE Related Features
- * This API is related with the following features :\n
+ * This function is related with the following features :\n
  *  - http://tizen.org/feature/nnstreamer.pipeline\n
  *
  * It is recommended to probe features in your application for reliability.\n
- * You can check if a device supports the related features for this API by using
+ * You can check if a device supports the related features for this function by using
  * @ref CAPI_SYSTEM_SYSTEM_INFO_MODULE, thereby controlling the procedure of
  * your application.\n
  * To ensure your application is only running on the device with specific