x86/dma: Remove dma_alloc_coherent_gfp_flags()

All dma_ops implementations used on x86 now take care of setting their own
required GFP_ masks for the allocation.  And given that the common code
now clears harmful flags itself that means we can stop the flags in all
the IOMMU implementations as well.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Jon Mason <jdmason@kudzu.us>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Muli Ben-Yehuda <mulix@mulix.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: iommu@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20180319103826.12853-10-hch@lst.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>