tmscim: remove unused SCSI_IRQ_NONE macro definition

This macro is only used in the NCR5380 drivers and they don't include
this header.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>