Rename polaris to corstone310

The polaris platform was renamed so the path
and name had to be updated.

Change-Id: I1c4aea9ab6c4311459a661a88054e7b88df16122
diff --git a/tfm_ci_pylib/tfm_build_manager.py b/tfm_ci_pylib/tfm_build_manager.py
index 27152a7..451ef41 100644
--- a/tfm_ci_pylib/tfm_build_manager.py
+++ b/tfm_ci_pylib/tfm_build_manager.py
@@ -45,7 +45,7 @@
                "arm/corstone1000":                    "corstone1000",
                "nxp/lpcxpresso55s69":                 "lpcxpresso55s69",
                "arm/mps3/an547":                      "AN547",
-               "arm/mps3/corstone_polaris":           "Polaris",
+               "arm/mps3/corstone310_fvp" :           "corstone310",
                "arm/mps3/an552":                      "AN552",
                "lairdconnectivity/bl5340_dvk_cpuapp": "BL5340",
                "nordic_nrf/nrf5340dk_nrf5340_cpuapp": "nrf5340dk",