For one GFP_DMA32 does not actually work with kmalloc, as we only have
GFP_DMA and GFP_KERNEL caches, but not GFP_DMA32.  Second the memory
is mapped using the proper DMA API anyway, which would include proper
bounce buffering if needed by the device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>