dma-direct: don't fail on highmem CMA pages in dma_direct_alloc_pages

dma-direct: don't fail on highmem CMA pages in dma_direct_alloc_pages

[ Upstream commit 92826e967535db2eb117db227b1191aaf98e4bb3 ]

When dma_direct_alloc_pages encounters a highmem page it just gives up
currently.  But what we really should do is to try memory using the
page allocator instead - without this platforms with a global highmem
CMA pool will fail all dma_alloc_pages allocations.

Fixes: efa70f2fdc84 ("dma-mapping: add a new dma_alloc_pages API")
Reported-by: Mark O'Neill <mao@tumblingdice.co.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>