Harmonise Doxygen comments in drivers, events, platform and rtos dirs

When a Doxygen group has been defined (created), all its needed to add
documentation to that group is `\addtogroup`. Since all the information
about the group is preserved, it is not necessary to mention the group
hierarchy again with `\ingroup`. This PR removes unnecessary Doxygen lines
across the `drivers`, `events`, `platform` and `rtos` directories.

It also ensures that new groups are created with `\defgroup` once and
referenced with `\addtogroup` whenever documentation needs to be added to
an existing group.

Author: hugueskamba

drivers/AnalogIn.h

@@ -28,7 +28,7 @@
 namespace mbed {
 /** \defgroup mbed-os-public Public API */
 
-/** \addtogroup drivers-public-api Drivers
+/** \defgroup drivers-public-api Drivers
  * \ingroup mbed-os-public
  */
 

drivers/AnalogOut.h

@@ -25,8 +25,6 @@
 #include "platform/PlatformMutex.h"
 
 namespace mbed {
-/** \addtogroup drivers-public-api */
-
 /**
  * \defgroup drivers_AnalogOut AnalogOut class
  * \ingroup drivers-public-api-gpio

drivers/Ethernet.h

@@ -23,9 +23,10 @@
 #if DEVICE_ETHERNET || defined(DOXYGEN_ONLY)
 
 namespace mbed {
-/** \ingroup mbed-os-public */
+
 /** \addtogroup drivers-public-api */
 /** @{*/
+
 /**
  * \defgroup drivers_Ethernet Ethernet class
  * @{

drivers/FlashIAP.h

@@ -49,9 +49,9 @@ extern uint32_t Load$$LR$$LR_IROM1$$Limit[];
 
 namespace mbed {
 
-/** \ingroup mbed-os-public */
 /** \addtogroup drivers-public-api */
 /** @{*/
+
 /**
  * \defgroup drivers_FlashIAP FlashIAP class
  * @{

drivers/I2CSlave.h

@@ -25,7 +25,7 @@
 
 namespace mbed {
 /**
- * \addtogroup drivers_I2CSlave I2CSlave class
+ * \defgroup drivers_I2CSlave I2CSlave class
  * \ingroup drivers-public-api-i2c
  * @{
  */

drivers/LowPowerTimeout.h

@@ -27,7 +27,7 @@
 
 namespace mbed {
 /**
- * \addtogroup drivers_LowPowerTimeout LowPowerTimeout class
+ * \defgroup drivers_LowPowerTimeout LowPowerTimeout class
  * \ingroup drivers-public-api-ticker
  * @{
  */

drivers/LowPowerTimer.h

@@ -27,7 +27,7 @@
 
 namespace mbed {
 /**
- * \addtogroup drivers_LowPowerTimer LowPowerTimer class
+ * \defgroup drivers_LowPowerTimer LowPowerTimer class
  * \ingroup drivers-public-api-ticker
  * @{
  */

drivers/MbedCRC.h

@@ -40,7 +40,6 @@ but we check for ( width < 8) before performing shift, so it should not be an is
 #endif
 
 namespace mbed {
-/** \ingroup mbed-os-public */
 /** \addtogroup drivers-public-api */
 /** @{*/
 /**

drivers/ResetReason.h

@@ -22,9 +22,9 @@
 #include "reset_reason_api.h"
 
 namespace mbed {
-/** \ingroup mbed-os-public */
 /** \addtogroup drivers-public-api */
 /** @{*/
+
 /**
  * \defgroup drivers_ResetReason ResetReason class
  * @{

drivers/SPI.h

@@ -46,7 +46,7 @@
 
 namespace mbed {
 /**
- * \addtogroup drivers_SPI SPI class
+ * \defgroup drivers_SPI SPI class
  * \ingroup drivers-public-api-spi
  * @{
  */