[Darwin, PPC, Mode Iterators 4/n] Update macho_high.

[Darwin, PPC, Mode Iterators 4/n] Update macho_high.

Drop the expander and use a mode iterator on the define_insn
for @macho_high_<mode> instead.

gcc/ChangeLog:

2019-09-28  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin.c (gen_macho_high): Amend to include the mode
	argument.
	(machopic_indirect_data_reference): Amend gen_macho_high call
	to include mode argument.
	(machopic_legitimize_pic_address): Likewise.
	* config/rs6000/rs6000.c (rs6000_legitimize_address):
	* config/rs6000/darwin.md (@macho_high_<mode>): New, replaces
	the macho_high expander and two define_insn entries.

From-SVN: r276256