Update SHA-224 documentation.

Rephrase config.h documentation and add a note to template
configs.

Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
diff --git a/configs/config-no-entropy.h b/configs/config-no-entropy.h
index d4948de..d0aef1d 100644
--- a/configs/config-no-entropy.h
+++ b/configs/config-no-entropy.h
@@ -73,6 +73,8 @@
 #define MBEDTLS_PK_WRITE_C
 #define MBEDTLS_PLATFORM_C
 #define MBEDTLS_RSA_C
+/* Library does not support enabling SHA-224 without SHA-256. Future version will
+ * have this option disabled by default. */
 #define MBEDTLS_SHA224_C
 #define MBEDTLS_SHA256_C
 #define MBEDTLS_SHA384_C