doxygen: group name all in lowcase (part 2) (#10530)

* doxygen: fs: unify groupname to lowercase

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

* doxygen: drivers: unify groupname to lowercase

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

* doxygen: signal: unify groupname to lowercase

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

---------

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

documentation/0.doxygen/components/filesystem.h

@@ -8,20 +8,20 @@
  */
 
 /**
- * @defgroup group_Fd File Descriptor
+ * @defgroup group_fs_file_descriptor File Descriptor
  *
  */
 
 /**
- * @defgroup group_FsApi File System API
+ * @defgroup group_fs_api File System API
  */
 
 /**
- * @defgroup group_FileApi File API
+ * @defgroup group_fs_file_api File API
  */
 
 /**
- * @defgroup group_FsPosixApi File POSIX API
+ * @defgroup group_fs_posix_api File POSIX API
  */
 
 /**@}*/

documentation/0.doxygen/core/ipc.h

@@ -8,7 +8,7 @@
  */
 
 /**
- * @defgroup group_Signal Signal
+ * @defgroup group_signal Signal
  * @brief signal is used for thread kill etc.
  *
  * A signal (also known as a soft interrupt signal), from a software perspective,

documentation/6.components/device-driver/audio/audio.md

@@ -6,7 +6,7 @@ The Audio device is a crucial component in embedded systems, responsible for aud
 
 ## API List
 
-For more details, see @ref group_Audio
+For more details, see @ref group_drivers_audio
 
 ## Audio Device Features