esp_scsi: make number of tags configurable

Add a field 'num_tags' to the esp structure to allow drivers
to overwrite the number of avialable tags if required.
Default is ESP_DEFAULT_TAGS.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h
index b5862e4..975d293 100644
--- a/drivers/scsi/esp_scsi.h
+++ b/drivers/scsi/esp_scsi.h
@@ -283,7 +283,6 @@
 	struct completion	*eh_done;
 };
 
-/* XXX make this configurable somehow XXX */
 #define ESP_DEFAULT_TAGS	16
 
 #define ESP_MAX_TARGET		16
@@ -445,7 +444,7 @@
 	u8			prev_soff;
 	u8			prev_stp;
 	u8			prev_cfg3;
-	u8			__pad;
+	u8			num_tags;
 
 	struct list_head	esp_cmd_pool;