ALSA: Enable CONFIG_ZONE_DMA for smaller PCI DMA masks
The PCI devices with DMA masks smaller than 32bit should enable
CONFIG_ZONE_DMA. Since the recent change of page allocator, page
allocations via dma_alloc_coherent() with the limited DMA mask bits
may fail more frequently, ended up with no available buffers, when
CONFIG_ZONE_DMA isn't enabled. With CONFIG_ZONE_DMA, the system has
much more chance to obtain such pages.