drm/amdgpu/mes10.1: add delay after mes engine enable

Add delay after mes engine enable, for it needs more time
to complete engine initialising.

Signed-off-by: Jack Xiao <Jack.Xiao@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>