drivers: crypto: Add authenticated decryption framework

Add framework for autheticated decryption of data. Currently this
patch optionally imports mbedtls library as a backend if build option
"DECRYPTION_SUPPORT = aes_gcm" is set to perform authenticated decryption
using AES-GCM algorithm.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Change-Id: I2966f0e79033151012bf4ffc66f484cd949e7271
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index f5bd298..06b334d 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -37,6 +37,15 @@
 #define ROTPK_NOT_DEPLOYED		(1 << 1)
 
 /*******************************************************************************
+ * plat_get_enc_key_info() flags
+ ******************************************************************************/
+/*
+ * Flag used to notify caller that information provided in key buffer is an
+ * identifier rather than an actual key.
+ */
+#define ENC_KEY_IS_IDENTIFIER		(1 << 0)
+
+/*******************************************************************************
  * Function declarations
  ******************************************************************************/
 /*******************************************************************************