Fix pretty printer of main_type.flds_bnds.bounds

In struct dynamic_prop the members kind and data were renamed to m_kind and
m_data.

And flag_upper_bound_is_count is actually in bounds directly, not in its
high member.

gdb/ChangeLog:

2021-01-02  Hannes Domani  <ssbssa@yahoo.de>

	* gdb-gdb.py.in: Fix main_type.flds_bnds.bounds pretty printer.