Simplify "want_partial_unit" handling

Simplify "want_partial_unit" handling

This changes the "want_partial_unit" parameters to have type bool, and
also removes the parameter from process_psymtab_comp_unit_reader.
This latter change seemed like an improvement, because it avoids a
pointless function call in the case where we are not planning to read
a partial unit.

2020-02-08  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.c (process_psymtab_comp_unit_reader): Remove
	"want_partial_unit" parameter.
	(process_psymtab_comp_unit): Change want_partial_unit to bool.
	Inline check for DW_TAG_partial_unit.
	(dwarf2_build_psymtabs_hard, scan_partial_symbols): Update.

Change-Id: I99e647f0c4faa3346e90a6e7bacc82af57eccff1