doc: release 3.6: no CACHE_MANAGEMENT by default on stm32h7/f7

Mentioning that stm32h7 and stm32F7 series do not have the
CONFIG_CACHE_MANAGEMENT by default. The application must
explicitly set CONFIG_CACHE_MANAGEMENT=y to activate
the cache (Icache, Dcache) on those stm32 series.

Signed-off-by: Francois Ramu <[email protected]>
(cherry picked from commit 1c59fa5)

Author: FRASTM

doc/releases/migration-guide-3.6.rst

@@ -46,6 +46,9 @@ Kernel
   :kconfig:option:`CONFIG_HEAP_MEM_POOL_IGNORE_MIN` option has been introduced (which defaults
   being disabled).
 
+* STM32H7 and STM32F7 should now activate the cache (Icache and Dcache) by setting explicitly
+  the  ``CONFIG_CACHE_MANAGEMENT`` to ``y``.
+
 Boards
 ******