btrfs: Drop __exit attribute on btrfs_exit_compress

As this function is called in some error paths while not
removing the module, the __exit attribute prevents the kernel
image from linking when btrfs is compiled in statically.
Signed-off-by: Alexey Charkov <alchark@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/compression.c

@@ -921,7 +921,7 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
 	return ret;
 }
 
-void __exit btrfs_exit_compress(void)
+void btrfs_exit_compress(void)
 {
 	free_workspaces();
 }