ia64: remove the unused sn_coherency_id symbol

The sn_coherency_id symbol isn't used anywhere, remove it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-23-hch@lst.de


Signed-off-by: Tony Luck <tony.luck@intel.com>