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>

services/std_svc/spm_deprecated/spm_main.c

@@ -151,7 +151,7 @@ static int32_t spm_init(void)
 
 	INFO("Secure Partition initialized.\n");
 
-	return rc;
+	return !rc;
 }
 
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