acfl: update the headers property (#44653)

Consistently with ArmPL@24:, the include directory for acfl@24:
has changed to include. The change wants to update to this change
and distinguish the include path for releases previous to 24.04
and the future ones

var/spack/repos/builtin/packages/acfl/package.py

@@ -378,6 +378,9 @@ def libs(self):
     def headers(self):
         armpl_dir = get_armpl_prefix(self.spec)
 
+        if self.spec.satisfies("@24:"):
+            suffix = "include"
+        else:
             suffix = "include" + self.lib_suffix
 
         incdir = join_path(armpl_dir, suffix)