amdgcn: Add instruction patterns for complex number operations.

gcc/ChangeLog:

	* config/gcn/gcn-protos.h (gcn_expand_dpp_swap_pairs_insn)
	(gcn_expand_dpp_distribute_even_insn)
	(gcn_expand_dpp_distribute_odd_insn): Declare.
	* config/gcn/gcn-valu.md (@dpp_swap_pairs<mode>)
	(@dpp_distribute_even<mode>, @dpp_distribute_odd<mode>)
	(cmul<conj_op><mode>3, cml<addsub_as><mode>4, vec_addsub<mode>3)
	(cadd<rot><mode>3, vec_fmaddsub<mode>4, vec_fmsubadd<mode>4)
	(fms<mode>4<exec>, fms<mode>4_negop2<exec>, fms<mode>4)
	(fms<mode>4_negop2): New patterns.
	* config/gcn/gcn.cc (gcn_expand_dpp_swap_pairs_insn)
	(gcn_expand_dpp_distribute_even_insn)
	(gcn_expand_dpp_distribute_odd_insn): New functions.
	* config/gcn/gcn.md: Add entries to unspec enum.

gcc/testsuite/ChangeLog:

	* gcc.target/gcn/complex.c: New test.