[PATCH 3/4] drm/vmwgfx: fix the check when to use dma_alloc_coherent

From: Christoph Hellwig Since Linux 4.21 we merged the swiotlb ops into the DMA direct ops, so they would always have a the sync_single methods. But late in the cicle we also removed the direct ops entirely, so we'd see NULL DMA ops. Switch vmw_dma_select_mode to only detect swiotlb presence us

[PATCH 3/4] drm/vmwgfx: fix the check when to use dma_alloc_coherent

Since Linux 4.21 we merged the swiotlb ops into the DMA direct ops, so they would always have a the sync_single methods. But late in the cicle we also removed the direct ops entirely, so we'd see NULL DMA ops. Switch vmw_dma_select_mode to only detect swiotlb presence using swiotlb_nr_tbl() inste