qcow2: Remove BDS parameter from qcow2_cache_discard()

This function was only using the BlockDriverState parameter to pass it
to qcow2_cache_get_table_idx() and qcow2_cache_table_release(). This
is no longer necessary so this parameter can be removed.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 9724f7e38e763ad3be32627c6b7fe8df9edb1476.1517840877.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/qcow2.h b/block/qcow2.h
index 867f2e8..7296784 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -656,7 +656,7 @@
 void qcow2_cache_put(Qcow2Cache *c, void **table);
 void *qcow2_cache_is_table_offset(BlockDriverState *bs, Qcow2Cache *c,
                                   uint64_t offset);
-void qcow2_cache_discard(BlockDriverState *bs, Qcow2Cache *c, void *table);
+void qcow2_cache_discard(Qcow2Cache *c, void *table);
 
 /* qcow2-bitmap.c functions */
 int qcow2_check_bitmaps_refcounts(BlockDriverState *bs, BdrvCheckResult *res,