drm/amdgpu: Fix size overflow

ttm->num_pages is uint32. Hit overflow when << PAGE_SHIFT directly

Fixes: 230c079fdc ("drm/ttm: make num_pages uint32_t")
Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -830,7 +830,7 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_device *bdev,
 
 	/* Allocate an SG array and squash pages into it */
 	r = sg_alloc_table_from_pages(ttm->sg, ttm->pages, ttm->num_pages, 0,
-				      ttm->num_pages << PAGE_SHIFT,
+				      (u64)ttm->num_pages << PAGE_SHIFT,
 				      GFP_KERNEL);
 	if (r)
 		goto release_sg;