[SCSI] pm8001: Fixes for tag alloc, error goto and code cleanup

Allocate right size for bitmap tag,fix error goto and cleanup print
message and undocable commemts. patch attached.

Signed-off-by: Lindar Liu <lindar_liu@usish.com>
Signed-off-by: Jack Wang <jack_wang@usish.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>