ANDROID: fuse-bpf: Fix build breakage without CONFIG_FUSE_BPF

Fix build error if CONFIG_FUSE_BPF not defined:

common/fs/fuse/file.c:2771:20: error: unused variable 'ff' [-Werror,-Wunused-variable]
2771 | struct fuse_file *ff = in->private_data;
| ^~
1 error generated.

Fixes: 5fb8f1c931c2 ("ANDROID: fuse-bpf: add bpf solution for splice read")
Change-Id: I43d194a1d326fd61c5faafbb524f6ca484fb29f6
Signed-off-by: Paul Lawrence <paullawrence@google.com>

fs/fuse/file.c

@@ -1843,9 +1843,9 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
 				struct pipe_inode_info *pipe, size_t len,
 				unsigned int flags)
 {
+#ifdef CONFIG_FUSE_BPF
 	struct fuse_file *ff = in->private_data;
 
-#ifdef CONFIG_FUSE_BPF
 	/* TODO - this is simply passthrough, not a proper BPF filter */
 	if (ff->backing_file)
 		return fuse_splice_read_backing(in, ppos, pipe, len, flags);