dma-mapping: replace dmam_alloc_noncoherent with dmam_alloc_attrs

dmam_alloc_noncoherent is a trivial wrapper around dmam_alloc_attrs,
that hardcodes one particular flag.  Make the devres code more
flexible by allowing the callers to pass arbitrary flags.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>