cdx: add MCDI protocol interface for firmware interaction

The MCDI (Management CPU Driver Interface) is used as a
protocol to communicate with the RPU firmware. It has
pre-defined set of messages for different message exchanges
between APU and RPU.

Signed-off-by: Puneet Gupta <puneet.gupta@amd.com>
Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
Signed-off-by: Tarak Reddy <tarak.reddy@amd.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Tested-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
Link: https://lore.kernel.org/r/20230313132636.31850-5-nipun.gupta@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/cdx/controller/Kconfig

@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# CDX controller configuration
+#
+# Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+#
+
+if CDX_BUS
+
+config MCDI_LOGGING
+	bool "MCDI Logging for the CDX controller"
+	depends on CDX_CONTROLLER
+	help
+	  Enable MCDI Logging for
+	  the CDX Controller for debug
+	  purpose.
+
+	  If unsure, say N.
+
+endif