Developed a new driver which allocates a 64bit memory on
each request in sequence order. At the moment, user queue
fence memory is the main consumer of this seq64 driver.

v2: Worked on review comments from Christian for the following
    modifications

    - Move driver name from "semaphore" to "seq64"
    - Remove unnecessary PT/PD mapping
    - Move enable_mes check into init/fini functions.

v3: Worked on review comments from Christian

    - drop enable_mes check
    - use DECLARE_BITMAP for bit array
    - added kerneldoc for seq64

v4: Worked on review comments from Christian
    - Rename amdgpu_seq64_get name with amdgpu_seq64_alloc

v5: Worked on review comments from Christian
    - Fix seq64 lockdep warning
    - move fpriv->seq64_va check into amdgpu_seq64_unmap()
    - make the function amdgpu_seq64_unmap() return as void.
    - reserve the buffers as not interruptible.

v6: port to drm_exec (Alex)
v7: disable for now (Arun)
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>