[IA64] remove superfluous layer from sn2 DMA API

When I converted the sn2 code over to the new DMA API, I left the old routines
in place and added wrappers to call them from the generic DMA API functions.
This added an unnecessary level of obfuscation since the generic ia64 code
calls those functions when any of the old style PCI DMA API functions are
called.  This patch rectifies the problem making the code much easier to
understand and hopefully a little more efficient (though I'm sure gcc was
already inlining things pretty well, there were a bunch of unnecessary checks
that I took this opportunity to remove).  It also shrinks the size of the sn2
pci_dma.c quite a bit.
 
  pci_dma.c |  480 +++++++++++++++++++-----------------------------------------
  1 files changed, 151 insertions(+), 329 deletions(-)
Signed-off-by: Jesse Barnes <jbarnes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>