Silence gcc 12.2.0 warning

Unfortunately this compiler complains about a variable potentially being
used un-initialized.  Silence the warning by initializing it to a sane
default.

Signed-off-by: Patrick Wildt <pwildt@google.com>
diff --git a/library/psa_crypto_cipher.c b/library/psa_crypto_cipher.c
index 881d673..3216c94 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -263,7 +263,7 @@
 {
     mbedtls_cipher_mode_t mode;
     psa_status_t status;
-    mbedtls_cipher_id_t cipher_id_tmp;
+    mbedtls_cipher_id_t cipher_id_tmp = MBEDTLS_CIPHER_ID_NONE;
 
     status = mbedtls_cipher_values_from_psa(alg, key_type, &key_bits, &mode, &cipher_id_tmp);
     if (status != PSA_SUCCESS) {