libxfs: create new files with attr forks if necessary

libxfs: create new files with attr forks if necessary

Create new files with attr forks if they're going to have parent
pointers.  In the next patch we'll fix mkfs to use the same parent
creation functions as the kernel, so we're going to need this.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>