yaffs: Cache object xattrib state.

yaffs: Cache object xattrib state.

We cache whether or not an object has xattributes.

This is done to get around the problem of the Linux VFS trying to check security
capabilities on every write. Assuming that most files don't have security
attributes, this code will save on a huge amount of reads and make writing
faster.

Signed-off-by: Charles Manning <cdhmanning@gmail.com>