btrfs: add fs_parameter definitions

In order to convert to the new mount API we have to change how we do the
mount option parsing.  For now we're going to duplicate these helpers to
make it easier to follow, and then remove the old code once everything
is in place.  This patch contains the re-definition of all of our mount
options into the new fs_parameter_spec format.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>