atari_NCR5380: Merge changes from NCR5380.c

In the past, atari_NCR5380.c was overlooked by those working on NCR5380.c
and this caused needless divergence. All of the changes in this patch were
taken from NCR5380.c.

This removes some unimportant discrepancies between the two core driver
forks so that 'diff' can be used to reveal the important ones, to
facilitate reunification.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>