linker: move app_smem.ld into include/linker

The app_smem.ld is also being used by architectures other than ARM.
So move the linker script out of include/arch/arm and into
include/linker.

Signed-off-by: Daniel Leung <[email protected]>

Author: dcpleung

CMakeLists.txt

@@ -1131,7 +1131,7 @@ configure_file(
      ${PROJECT_BINARY_DIR}/include/generated/app_data_alignment.ld)
 
 configure_file(
-     $ENV{ZEPHYR_BASE}/include/arch/arm/cortex_m/scripts/app_smem.ld
+     $ENV{ZEPHYR_BASE}/include/linker/app_smem.ld
      ${PROJECT_BINARY_DIR}/include/generated/app_smem.ld)
 
 if(CONFIG_USERSPACE)