tpm: Make use of TPM2_ALG_INVAL from enum

Now that the enum includes TPM2_ALG_INVAL, use that name in the
code.

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/cmd/tpm-v2.c b/cmd/tpm-v2.c
index a62862e..346e21d 100644
--- a/cmd/tpm-v2.c
+++ b/cmd/tpm-v2.c
@@ -113,7 +113,7 @@
 		return CMD_RET_USAGE;
 	if (argc == 4) {
 		algo = tpm2_name_to_algorithm(argv[3]);
-		if (algo < 0)
+		if (algo == TPM2_ALG_INVAL)
 			return CMD_RET_FAILURE;
 	}
 	algo_len = tpm2_algorithm_to_len(algo);
@@ -157,7 +157,7 @@
 		return CMD_RET_USAGE;
 	if (argc == 4) {
 		algo = tpm2_name_to_algorithm(argv[3]);
-		if (algo < 0)
+		if (algo == TPM2_ALG_INVAL)
 			return CMD_RET_FAILURE;
 	}
 	algo_len = tpm2_algorithm_to_len(algo);
@@ -288,7 +288,7 @@
 		return CMD_RET_USAGE;
 
 	algo = tpm2_name_to_algorithm(argv[1]);
-	if (algo == -EINVAL)
+	if (algo == TPM2_ALG_INVAL)
 		return CMD_RET_USAGE;
 
 	ret = get_tpm(&dev);