drm/amdgpu: add usermode queue base code

This patch adds IP independent skeleton code for amdgpu
usermode queue. It contains:
- A new files with init functions of usermode queues.
- A queue context manager in driver private data.

V1: Worked on design review comments from RFC patch series:
(https://patchwork.freedesktop.org/series/112214/)
- Alex: Keep a list of queues, instead of single queue per process.
- Christian: Use the queue manager instead of global ptrs,
           Don't keep the queue structure in amdgpu_ctx

V2:
 - Reformatted code, split the big patch into two

V3:
- Integration with doorbell manager

V4:
- Align the structure member names to the largest member's column
  (Luben)
- Added SPDX license (Luben)

V5:
- Do not add amdgpu.h in amdgpu_userqueue.h (Christian).
- Move struct amdgpu_userq_mgr into amdgpu_userqueue.h (Christian).

V6: Rebase
V9: Rebase
V10: Rebase + Alex's R-B

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_userqueue.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2023 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include "amdgpu.h"
+
+int amdgpu_userq_mgr_init(struct amdgpu_userq_mgr *userq_mgr, struct amdgpu_device *adev)
+{
+	mutex_init(&userq_mgr->userq_mutex);
+	idr_init_base(&userq_mgr->userq_idr, 1);
+	userq_mgr->adev = adev;
+
+	return 0;
+}
+
+void amdgpu_userq_mgr_fini(struct amdgpu_userq_mgr *userq_mgr)
+{
+	idr_destroy(&userq_mgr->userq_idr);
+	mutex_destroy(&userq_mgr->userq_mutex);
+}