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 93a6b93..173ca29 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -26,7 +26,7 @@
     mbedtls_cipher_id_t *cipher_id)
 {
     mbedtls_cipher_mode_t mode;
-    mbedtls_cipher_id_t cipher_id_tmp;
+    mbedtls_cipher_id_t cipher_id_tmp = MBEDTLS_CIPHER_ID_NONE;
 
     if (PSA_ALG_IS_AEAD(alg)) {
         alg = PSA_ALG_AEAD_WITH_SHORTENED_TAG(alg, 0);