configure: make --iasl option actually work

--iasl option was added to CC option parsing section by mistake,
it's not effective there and attempts to use cause
an 'unknown option' error.

Fix this up.

Tested-by: Marcel Apfelbaum <marcel.a@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

configure

@@ -272,8 +272,6 @@ for opt do
   ;;
   --cxx=*) CXX="$optarg"
   ;;
-  --iasl=*) iasl="$optarg"
-  ;;
   --source-path=*) source_path="$optarg"
   ;;
   --cpu=*) cpu="$optarg"
@@ -649,6 +647,8 @@ for opt do
   ;;
   --cxx=*)
   ;;
+  --iasl=*) iasl="$optarg"
+  ;;
   --objcc=*) objcc="$optarg"
   ;;
   --make=*) make="$optarg"