doc: Update 1.9 release notes for arm

Adds arm items to the architectures and boards sections.

Signed-off-by: Maureen Helm <[email protected]>

Author: MaureenHelm

doc/release-notes-1.9.rst

@@ -38,13 +38,22 @@ Kernel
 Architectures
 *************
 
-* change description
+* arm: Added STM32F405, STM32F417, STM32F103x8 SoCs
+* arm: Added TI CC2650 SoC
+* arm: Removed TI CC3200 SoC
+* arm: Added MPU support to nRF52, STM32L4, and STM32F3
 
 Boards
 ******
 
 * Added device tree support for Intel Quark based microcontroller boards
   such as Arduino_101, tinytile, and Quark_d2000_crb.
+* arm: Added Atmel SAM4S Xplained board
+* arm: Added Olimex STM32-E407 and STM32-P405 boards
+* arm: Added STM32F412 Nucleo and STM32F429I-DISC1 boards
+* arm: Added TI SensorTag board
+* arm: Removed TI CC3200 LaunchXL board
+* arm: Added VBLUno51 and VBLUno52 boards
 
 Drivers and Sensors
 *******************