drm/msm: move domain allocation into msm_iommu_new()

drm/msm: move domain allocation into msm_iommu_new()

After the msm_iommu instance is created, the IOMMU domain is completely
handled inside the msm_iommu code. Move the iommu_domain_alloc() call
into the msm_iommu_new() to simplify callers code.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/509615/
Link: https://lore.kernel.org/r/20221102175449.452283-2-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>