Squashfs: optimise squashfs_cache_get entry search

squashfs_cache_get() iterates over all entries to search for
 block its looking for. Often get() / put() are called for
 same block.

If we cache the current entry index, then we can optimise the
subsequent *_get() calls.

Signed-off-by: Ajeet Yadav <ajeet.yadav.77@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
diff --git a/fs/squashfs/squashfs_fs_sb.h b/fs/squashfs/squashfs_fs_sb.h
index 651f0b3..52934a2 100644
--- a/fs/squashfs/squashfs_fs_sb.h
+++ b/fs/squashfs/squashfs_fs_sb.h
@@ -28,6 +28,7 @@
 struct squashfs_cache {
 	char			*name;
 	int			entries;
+	int			curr_blk;
 	int			next_blk;
 	int			num_waiters;
 	int			unused;