Add PSA config for ChaCha20

Add checks for PSA_WANT_KEY_TYPE_CHACHA20, both with and without
MBEDTLS_PSA_CRYPTO_CONFIG.  This only adds support for the ciphers
itself, presumably as a stream cipher (and not yet AEAD).

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/include/mbedtls/config_psa.h b/include/mbedtls/config_psa.h
index b6bc6f3..76db6c7 100644
--- a/include/mbedtls/config_psa.h
+++ b/include/mbedtls/config_psa.h
@@ -266,6 +266,13 @@
 #endif /*!MBEDTLS_PSA_ACCEL_KEY_TYPE_DES || PSA_HAVE_SOFT_BLOCK_MODE */
 #endif /* PSA_WANT_KEY_TYPE_DES */
 
+#if defined(PSA_WANT_KEY_TYPE_CHACHA20)
+#if !defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_CHACHA20)
+#define MBEDTLS_PSA_BUILTIN_KEY_TYPE_CHACHA20 1
+#define MBEDTLS_CHACHA20_C
+#endif /*!MBEDTLS_PSA_ACCEL_KEY_TYPE_CHACHA20 */
+#endif /* PSA_WANT_KEY_TYPE_CHACHA20 */
+
 #if defined(PSA_WANT_ALG_STREAM_CIPHER)
 #define MBEDTLS_PSA_BUILTIN_ALG_STREAM_CIPHER 1
 #endif /* PSA_WANT_ALG_STREAM_CIPHER */
@@ -483,6 +490,13 @@
 #define MBEDTLS_PSA_BUILTIN_KEY_TYPE_DES 1
 #endif
 
+#if defined(MBEDTLS_CHACHA20_C)
+#define PSA_WANT_KEY_TYPE_CHACHA20 1
+#define PSA_WANT_ALG_STREAM_CIPHER 1
+#define MBEDTLS_PSA_BUILTIN_KEY_TYPE_CHACHA20 1
+#define MBEDTLS_PSA_BUILTIN_ALG_STREAM_CIPHER 1
+#endif
+
 #if defined(MBEDTLS_CIPHER_MODE_CBC)
 #define PSA_WANT_ALG_CBC_NO_PADDING 1
 #if defined(MBEDTLS_CIPHER_PADDING_PKCS7)