Add support for Cortex-M85

Rely on CMSIS code for initializing Cortex-M85 devices.

Fallback to mcpu=cortex-m55 for gcc until support for cortex-m85 is
available.

Change-Id: I8b47563c3f0f44e35735a569f2abf8a308948e67
diff --git a/targets/corstone-310/CMakeLists.txt b/targets/corstone-310/CMakeLists.txt
index 446a424..5583e3c 100644
--- a/targets/corstone-310/CMakeLists.txt
+++ b/targets/corstone-310/CMakeLists.txt
@@ -20,8 +20,7 @@
 # Default parameters
 #############################################################################
 
-# TODO Olympus CPU is backwards compatible with Cortex-M55
-set(TARGET_CPU "cortex-m55" CACHE INTERNAL "")
+set(TARGET_CPU "cortex-m85" CACHE INTERNAL "")
 
 if (NOT CMAKE_TOOLCHAIN_FILE)
     set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/toolchain/armclang.cmake")