drm/msm: fix IOMMU cleanup for -EPROBE_DEFER

If probe fails after IOMMU is attached, we need to detach in order to
clean up properly.  Before this change, IOMMU faults would occur if the
probe failed (-EPROBE_DEFER).

Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_mmu.h b/drivers/gpu/drm/msm/msm_mmu.h
index 0303244..21da6d1 100644
--- a/drivers/gpu/drm/msm/msm_mmu.h
+++ b/drivers/gpu/drm/msm/msm_mmu.h
@@ -22,6 +22,7 @@
 
 struct msm_mmu_funcs {
 	int (*attach)(struct msm_mmu *mmu, const char **names, int cnt);
+	void (*detach)(struct msm_mmu *mmu, const char **names, int cnt);
 	int (*map)(struct msm_mmu *mmu, uint32_t iova, struct sg_table *sgt,
 			unsigned len, int prot);
 	int (*unmap)(struct msm_mmu *mmu, uint32_t iova, struct sg_table *sgt,