swiotlb: use dma_capable()

This converts swiotlb to use dma_capable() instead of
swiotlb_arch_address_needs_mapping() and is_buffer_dma_capable().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Becky Bruce <beckyb@kernel.crashing.org>