crypto: ccp - Add support for an interface for platform features

Some platforms with a PSP support an interface for features that
interact directly with the PSP instead of through a SEV or TEE
environment.

Initialize this interface so that other drivers can consume it.
These drivers may either be subdrivers for the ccp module or
external modules.  For external modules, export a symbol for them
to utilize.

Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ccp/platform-access.h

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) Platform Access interface
+ *
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ *
+ * Author: Mario Limonciello <mario.limonciello@amd.com>
+ */
+
+#ifndef __PSP_PLATFORM_ACCESS_H__
+#define __PSP_PLATFORM_ACCESS_H__
+
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/psp-platform-access.h>
+
+#include "psp-dev.h"
+
+struct psp_platform_access_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	struct platform_access_vdata *vdata;
+
+	struct mutex mailbox_mutex;
+
+	void *platform_access_data;
+};
+
+void platform_access_dev_destroy(struct psp_device *psp);
+int platform_access_dev_init(struct psp_device *psp);
+
+#endif /* __PSP_PLATFORM_ACCESS_H__ */