Btrfs: fix the new inspection ioctls for 32 bit compat

The new ioctls to follow backrefs are not clean for 32/64 bit
compat.  This reworks them for u64s everywhere.  They are brand new, so
there are no problems with changing the interface now.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 94cd3a1..562dad1 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -272,7 +272,7 @@
 			swarn->logical, swarn->dev->name,
 			(unsigned long long)swarn->sector, root, inum, offset,
 			min(isize - offset, (u64)PAGE_SIZE), nlink,
-			ipath->fspath->str[i]);
+			(char *)ipath->fspath->val[i]);
 
 	free_ipath(ipath);
 	return 0;