libxfs: pass flags2 from parent to child when creating files

libxfs: pass flags2 from parent to child when creating files

When mkfs creates a new file as a child of an existing directory, we
should propagate the flags2 field from parent to child like the kernel
does.  This ensures that mkfs propagates cowextsize hints properly when
protofiles are in use.

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