drm/amdkfd: Correct partial migration virtual addr

Partial migration to system memory should use migrate.addr, not
prange->start as virtual address to allocate system memory page.

Fixes: a546a276 ("drm/amdkfd: Use partial migrations/mapping for GPU/CPU page faults in SVM")
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Xiaogang Chen <Xiaogang.Chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_migrate.c

@@ -574,7 +574,7 @@ svm_migrate_copy_to_ram(struct amdgpu_device *adev, struct svm_range *prange,
 	pr_debug("svms 0x%p [0x%lx 0x%lx]\n", prange->svms, prange->start,
 		 prange->last);
 
-	addr = prange->start << PAGE_SHIFT;
+	addr = migrate->start;
 
 	src = (uint64_t *)(scratch + npages);
 	dst = scratch;