drm/amdgpu: add new IOCTL for usermode queue

This patch adds:
- A new IOCTL function to create and destroy
- A new structure to keep all the user queue data in one place.
- A function to generate unique index for the queue.

V1: Worked on review comments from RFC patch series:
  - 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: Worked on review comments:
 - Christian:
   - Formatting of text
   - There is no need for queuing of userqueues, with idr in place
 - Alex:
   - Remove use_doorbell, its unnecessary
   - Reuse amdgpu_mqd_props for saving mqd fields

 - Code formatting and re-arrangement

V3:
 - Integration with doorbell manager

V4:
 - Accommodate MQD union related changes in UAPI (Alex)
 - Do not set the queue size twice (Bas)

V5:
 - Remove wrapper functions for queue indexing (Christian)
 - Do not save the queue id/idr in queue itself (Christian)
 - Move the idr allocation in the IP independent generic space
  (Christian)

V6:
 - Check the validity of input IP type (Christian)

V7:
 - Move uq_func from uq_mgr to adev (Alex)
 - Add missing free(queue) for error cases (Yifan)

V9:
 - Rebase

V10: Addressed review comments from Christian, and added R-B:
 - Do not initialize the local variable
 - Convert DRM_ERROR to DEBUG.

V11:
  - check the input flags to be zero (Alex)

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Reviewed-by: Christian Koenig <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>