btrfs: cleanup 64bit/32bit divs, provably bounded values

The divisor is derived from nodesize or PAGE_SIZE, fits into 32bit type.
Get rid of a few more do_div instances.

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0a9fe21..4a5524c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1564,7 +1564,7 @@
 		goto out_free;
 	}
 
-	do_div(new_size, root->sectorsize);
+	new_size = div_u64(new_size, root->sectorsize);
 	new_size *= root->sectorsize;
 
 	printk_in_rcu(KERN_INFO "BTRFS: new size for %s is %llu\n",