SPM: Fix missing break in TFM_SVC_OUTPUT_UNPRIV_STRING SVC handling

Missing break statement when handling TFM_SVC_OUTPUT_UNPRIV_STRING
in Library mode

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: I13cee7e29a6879856f3a395ff36f223c994a395a
diff --git a/secure_fw/spm/cmsis_func/tfm_core_svcalls_func.c b/secure_fw/spm/cmsis_func/tfm_core_svcalls_func.c
index f6407e5..879f991 100644
--- a/secure_fw/spm/cmsis_func/tfm_core_svcalls_func.c
+++ b/secure_fw/spm/cmsis_func/tfm_core_svcalls_func.c
@@ -97,6 +97,7 @@
     case TFM_SVC_OUTPUT_UNPRIV_STRING:
         svc_args[0] = tfm_hal_output_spm_log((const char *)svc_args[0],
                                              svc_args[1]);
+        break;
 #endif
     default:
 #ifdef PLATFORM_SVC_HANDLERS