test_driver_key_management: rename counter for export_public_key() hits

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/include/test/drivers/key_management.h b/tests/include/test/drivers/key_management.h
index 24ecbc3..526adbb 100644
--- a/tests/include/test/drivers/key_management.h
+++ b/tests/include/test/drivers/key_management.h
@@ -27,7 +27,7 @@
      * is called. */
     unsigned long hits;
     /* Subset of hits which only counts key operations with EC key */
-    unsigned long export_public_key_hits;
+    unsigned long hits_export_public_key;
     /* Location of the last key management driver called to import a key. */
     psa_key_location_t location;
 } mbedtls_test_driver_key_management_hooks_t;