CMake platform: remove IAR related CMakeLists

Not supported

Author: 0xc0170

platform/source/CMakeLists.txt

@@ -1,9 +1,7 @@
 # Copyright (c) 2020 ARM Limited. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
-if("CORTEX_A" IN_LIST MBED_TARGET_LABELS)
-    add_subdirectory(TARGET_CORTEX_A)
-elseif("CORTEX_M" IN_LIST MBED_TARGET_LABELS)
+if("CORTEX_M" IN_LIST MBED_TARGET_LABELS)
     add_subdirectory(TARGET_CORTEX_M)
 endif()