Remove init_psymbol_list

Remove init_psymbol_list

init_psymbol_list is now empty, and so this removes it.

gdb/ChangeLog
2020-11-01  Tom Tromey  <tom@tromey.com>

	* dbxread.c (dbx_symfile_read): Update.
	* dwarf2/read.c (dwarf2_build_psymtabs): Update.
	* xcoffread.c (xcoff_initial_scan): Update.
	* psympriv.h (init_psymbol_list): Don't declare.
	* psymtab.c (init_psymbol_list): Remove.