fix(doc): update xpack url

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

README.md

@@ -28,7 +28,9 @@ This porting is based on:
     * The Low-Layer (LL) APIs, a light-weight, optimized, expert oriented set of APIs designed for both performance and runtime efficiency
     * CMSIS device definition for STM32
 * [CMSIS](https://developer.arm.com/embedded/cmsis): Cortex Microcontroller Software Interface Standard (CMSIS) is a vendor-independent hardware abstraction layer for the Cortex®-M processor series and defines generic tool interfaces. It has been packaged as a module for Arduino IDE: https://github.com/stm32duino/ArduinoModule-CMSIS
-* [GNU Arm Embedded Toolchain](https://developer.arm.com/open-source/gnu-toolchain/gnu-rm): Arm Embedded GCC compiler, libraries and other GNU tools necessary for bare-metal software development on devices based on the Arm Cortex-M. Packages are provided thanks [The xPack GNU Arm Embedded GCC](https://xpack.github.io/arm-none-eabi-gcc/): https://github.com/xpack-dev-tools/arm-none-eabi-gcc-xpack
+* [GNU Arm Embedded Toolchain](https://developer.arm.com/open-source/gnu-toolchain/gnu-rm): Arm Embedded GCC compiler, libraries and other GNU tools necessary for bare-metal software development on devices based on the Arm Cortex-M. Packages are provided thanks [The xPack 3rd Party Development Tools](https://github.com/xpack-dev-tools/):
+  * https://github.com/xpack-dev-tools/arm-none-eabi-gcc-xpack
+  * https://github.com/xpack-dev-tools/openocd-xpack
 
 ## Getting Started