testcase: update integration platform name

The Zephyr Project has introduced Hardware Model Version 2.
As a result, the platform name 'mps2_an385' in Zephyr
has been changed.
Therefore, it is necessary to update the platform name
in the test case as well.

Signed-off-by: Gaetan Perrot <[email protected]>

testcase.yaml

@@ -2,5 +2,5 @@ tests:
   libcsp.subsec:
     integration_platforms:
       - qemu_cortex_m3
-      - mps2_an385
+      - mps2/an385
     tags: libcsp