Fix wrong flag ASSERT in xfs_attr_shortform_getvalue

This ASSERT is testing an if_flags flag value against
a di_aformat enum value.  di_aformat is never assigned
XFS_IFINLINE.

This happens to work for now, because XFS_IFINLINE has
the same value as XFS_DINODE_FMT_LOCAL, and that's tested
just before we call this function.

However, I think the intention is to assert that we have
read in the data, i.e. XFS_IFINLINE on if_flags, before
we use if_data.  This is done in other places through the
code as well.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ben Myers <bpm@sgi.com>