drm/amdgpu: map wptr BO into GART

drm/amdgpu: map wptr BO into GART

To support oversubscription, MES FW expects WPTR BOs to
be mapped into GART, before they are submitted to usermode
queues. This patch adds a function for the same.

V4: fix the wptr value before mapping lookup (Bas, Christian).

V5: Addressed review comments from Christian:
    - Either pin object or allocate from GART, but not both.
    - All the handling must be done with the VM locks held.

V7: Addressed review comments from Christian:
    - Do not take vm->eviction_lock
    - Use amdgpu_bo_gpu_offset to get the wptr_bo GPU offset

V8:  Rebase
V9:  Changed the function names from gfx_v11* to mes_v11*
V10: Remove unused adev (Harish)

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