Fix DAC960 driver on machines which don't support 64-bit DMA

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=8942

Use PCI_DMA_* constants instead of own private definitions Fall back to
32-bit DMA mask if a 64-bit one fails

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Acked-by: Jeff Garzik <jeff@garzik.org>
Tested-by: Lars <polynomial-c@gmx.de>
Cc: Alessandro Polverini <alex@nibbles.it>
Cc: <dac@conglom-o.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>