services/spm_deprecated: fix return code polarity of spm_init()

Registered init handlers return a boolean int, not a return code,
so convert the result from the SPM init call before returning it.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
diff --git a/services/std_svc/spm_deprecated/spm_main.c b/services/std_svc/spm_deprecated/spm_main.c
index 540f257..7525763 100644
--- a/services/std_svc/spm_deprecated/spm_main.c
+++ b/services/std_svc/spm_deprecated/spm_main.c
@@ -151,7 +151,7 @@
 
 	INFO("Secure Partition initialized.\n");
 
-	return rc;
+	return !rc;
 }
 
 /*******************************************************************************