doc/stm32f4discovery: Improve the page, add board picture

This commits improves a little bit the STM32F4Discovery documentation
page.

Signed-off-by: Alan C. Assis <acassis@gmail.com>

Documentation/platforms/arm/stm32f4/boards/stm32f4discovery/index.rst

@@ -4,17 +4,30 @@ ST STM32F4-Discovery
 
 .. tags:: chip:stm32, chip:stm32f4, chip:stm32f407
 
-This page discusses issues unique to NuttX configurations for the
-STMicro STM32F4Discovery development board featuring the STM32F407VGT6
-MCU. The STM32F407VGT6 is a 168MHz Cortex-M4 operation with 1Mbit Flash
-memory and 128kbytes. The board features:
+The STM32F4Discover board (also known as STM32F407G-DISC1) is a low cost
+development board released by STMicroelectronics.
 
+.. figure:: stm32f4discovery.png
+   :align: center
+
+Features
+========
+
+- Processor
+    - STM32F407VGT6 (Cortex-M4 running at 168MHz)
+- Memory
+    - 192 KiB SRAM memory
+    - 1024 MiB Flash
+- Connectivity
+    - USB host/device (OTG) over Micro-AB connector 
+    - Note: the board also supports Ethernet, CAN, RS485 (but requires baseboard)
+- Multimedia
+    - Audio Input and Output (over P2 connector)
 - On-board ST-LINK/V2 for programming and debugging,
 - LIS302DL, ST MEMS motion sensor, 3-axis digital output accelerometer,
 - MP45DT02, ST MEMS audio sensor, omni-directional digital microphone,
 - CS43L22, audio DAC with integrated class D speaker driver,
 - Four user LEDs and two push-buttons,
-- USB OTG FS with micro-AB connector, and
 - Easy access to most MCU pins.
 
 Refer to http://www.st.com/internet/evalboard/product/252419.jsp for