xfs: move xfs_fc_get_tree() above xfs_fc_reconfigure()

Grouping the options parsing and mount handling functions above the
struct fs_context_operations but below the struct super_operations
should improve (some) the grouping of the super operations while also
improving the grouping of the options parsing and mount handling code.

Now move xfs_fc_get_tree() and friends, also take the oppertunity to
change STATIC to static for the xfs_fs_put_super() function.
This is a straight code move, there aren't any functional changes.

Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>