s390/cio: fix multiple structure definitions

Fix multiple definitions of struct channel_path_desc by moving it
to asm/chpid.h . Also change ccw_device_get_chp_desc to use proper
types.

Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/chp.c b/drivers/s390/cio/chp.c
index 6c440d4..d497aa0 100644
--- a/drivers/s390/cio/chp.c
+++ b/drivers/s390/cio/chp.c
@@ -509,7 +509,7 @@
  * On success return a newly allocated copy of the channel-path description
  * data associated with the given channel-path ID. Return %NULL on error.
  */
-void *chp_get_chp_desc(struct chp_id chpid)
+struct channel_path_desc *chp_get_chp_desc(struct chp_id chpid)
 {
 	struct channel_path *chp;
 	struct channel_path_desc *desc;