atari_NCR5380: Move static TagAlloc array to host data

The atari_NCR5380.c core driver keeps some per-host data in a static
variable which limits the driver to a single instance. Fix this by moving
TagAlloc to the hostdata struct.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>