Error codes for hardware accelerator failures

Add MBEDTLS_ERR_XXX_HW_ACCEL_FAILED error codes for all cryptography
modules where the software implementation can be replaced by a hardware
implementation.

This does not include the individual message digest modules since they
currently have no way to return error codes.

This does include the higher-level md, cipher and pk modules since
alternative implementations and even algorithms can be plugged in at
runtime.
diff --git a/include/mbedtls/camellia.h b/include/mbedtls/camellia.h
index 107056f..cf07629 100644
--- a/include/mbedtls/camellia.h
+++ b/include/mbedtls/camellia.h
@@ -38,6 +38,7 @@
 
 #define MBEDTLS_ERR_CAMELLIA_INVALID_KEY_LENGTH           -0x0024  /**< Invalid key length. */
 #define MBEDTLS_ERR_CAMELLIA_INVALID_INPUT_LENGTH         -0x0026  /**< Invalid data input length. */
+#define MBEDTLS_ERR_CAMELLIA_HW_ACCEL_FAILED              -0x0027  /**< Camellia hardware accelerator failed. */
 
 #if !defined(MBEDTLS_CAMELLIA_ALT)
 // Regular implementation