release-notes: 4.4: add new voltage-scale property for STM32U5 PWRC

Add new voltage scale selection property for STM32U5 to 4.4 release notes.

Signed-off-by: Mathieu Choplain <mathieu.choplain-ext@st.com>

Author: mathieuchopstm

doc/releases/release-notes-4.4.rst

@@ -117,6 +117,12 @@ New APIs and options
     * :kconfig:option:`CONFIG_NVMEM_FLASH`
     * :kconfig:option:`CONFIG_NVMEM_FLASH_WRITE`
 
+* Power
+
+  * The new ``voltage-scale`` property of :dtcompatible:`st,stm32u5-pwr` can be used to
+    select the voltage scale manually on STM32U5 series via Devicetree. This notably
+    enables usage of the USB controller at lower system clock frequencies.
+
 * Settings
 
    * :kconfig:option:`CONFIG_SETTINGS_SAVE_SINGLE_SUBTREE_WITHOUT_MODIFICATION`