drm/amdgpu: remove excess function parameter

Fix below htmldocs build warning:

"warning: Excess function parameter 'vm_context' description in 'amdgpu_vm_init'"
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -2796,7 +2796,6 @@ long amdgpu_vm_wait_idle(struct amdgpu_vm *vm, long timeout)
  *
  * @adev: amdgpu_device pointer
  * @vm: requested vm
- * @vm_context: Indicates if it GFX or Compute context
  * @pasid: Process address space identifier
  *
  * Init @vm fields.