modules: cmsis: only add cmsis path for Cortex A and R

The cmsis module is not supposed to be used for Cortex M, where cmsis_6
should be used instead, but the build system currently still adds the
cmsis header directly in the include path if the module is present and
we are building for Cortex M, this means a PR could still use the old
headers, the CI would not catch it but then it would fail if an
application only has cmsis_6 available.

Fix this by moving the CMake add_subdirectory directory in the existing
conditional for Cortex A and R.

Signed-off-by: Fabio Baltieri <[email protected]>

Author: fabiobaltieri

modules/cmsis/CMakeLists.txt

@@ -1,8 +1,7 @@
 # Copyright (c) 2023 Nordic Semiconductor ASA
 # SPDX-License-Identifier: Apache-2.0
 
-add_subdirectory(${ZEPHYR_CURRENT_MODULE_DIR} cmsis)
-
 if(CONFIG_CPU_AARCH32_CORTEX_A OR CONFIG_CPU_AARCH32_CORTEX_R)
+  add_subdirectory(${ZEPHYR_CURRENT_MODULE_DIR} cmsis)
   zephyr_include_directories(.)
 endif()