btrfs: cleanup ino cache members of btrfs_root

The naming is confusing, generic yet used for a specific cache. Add a
prefix 'ino_' or rename appropriately.

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8e29b61..a835a54 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1776,12 +1776,12 @@
 
 	/* free ino cache stuff */
 	struct btrfs_free_space_ctl *free_ino_ctl;
-	enum btrfs_caching_type cached;
-	spinlock_t cache_lock;
-	wait_queue_head_t cache_wait;
+	enum btrfs_caching_type ino_cache_state;
+	spinlock_t ino_cache_lock;
+	wait_queue_head_t ino_cache_wait;
 	struct btrfs_free_space_ctl *free_ino_pinned;
-	u64 cache_progress;
-	struct inode *cache_inode;
+	u64 ino_cache_progress;
+	struct inode *ino_cache_inode;
 
 	struct mutex log_mutex;
 	wait_queue_head_t log_writer_wait;