iommu: arm-smmu-impl: Add 8250 display compatible to the client list.

Required for turning on per-process page tables for the GPU.

Signed-off-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20220614230136.3726047-1-emma@anholt.net
Signed-off-by: Will Deacon <will@kernel.org>