dm snapshot: rename dm_snap_exception to dm_exception

The exception structure is not necessarily just a snapshot
element (especially after we pull it out of dm-snap.c).

Renaming appropriately.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 7e855fb..24b8acd 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -580,7 +580,7 @@
 }
 
 static int persistent_prepare_exception(struct dm_exception_store *store,
-					struct dm_snap_exception *e)
+					struct dm_exception *e)
 {
 	struct pstore *ps = get_info(store);
 	uint32_t stride;
@@ -607,7 +607,7 @@
 }
 
 static void persistent_commit_exception(struct dm_exception_store *store,
-					struct dm_snap_exception *e,
+					struct dm_exception *e,
 					void (*callback) (void *, int success),
 					void *callback_context)
 {