Do not look at file symbols when reading psymtabs

Do not look at file symbols when reading psymtabs

The DWARF reader was setting the list_in_scope member when reading
partial symbols.  however, this member is only useful when reading
full symbols.  Future patches will make this assert, so remove these
unneeded initializations.

gdb/ChangeLog
2018-07-20  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (process_psymtab_comp_unit_reader)
	(build_type_psymtabs_reader): Do not set list_in_scope.