amdgcn: Add gfx1036 target

Add support for the gfx1036 RDNA2 APU integrated graphics devices.  The ROCm
documentation warns that these may not be supported, but it seems to work
at least partially.

gcc/ChangeLog:

	* config.gcc (amdgcn): Add gfx1036 entries.
	* config/gcn/gcn-hsa.h (NO_XNACK): Likewise.
	(gcn_local_sym_hash): Likewise.
	* config/gcn/gcn-opts.h (enum processor_type): Likewise.
	(TARGET_GFX1036): New macro.
	* config/gcn/gcn.cc (gcn_option_override): Handle gfx1036.
	(gcn_omp_device_kind_arch_isa): Likewise.
	(output_file_start): Likewise.
	* config/gcn/gcn.h (TARGET_CPU_CPP_BUILTINS): Add __gfx1036__.
	(TARGET_CPU_CPP_BUILTINS): Rename __gfx1030 to __gfx1030__.
	* config/gcn/gcn.opt: Add gfx1036.
	* config/gcn/mkoffload.cc (EF_AMDGPU_MACH_AMDGCN_GFX1036): New.
	(main): Handle gfx1036.
	* config/gcn/t-omp-device: Add gfx1036 isa.
	* doc/install.texi (amdgcn): Add gfx1036.
	* doc/invoke.texi (-march): Likewise.

libgomp/ChangeLog:

	* plugin/plugin-gcn.c (EF_AMDGPU_MACH): GFX1036.
	(gcn_gfx1103_s): New.
	(isa_hsa_name): Handle gfx1036.
	(isa_code): Likewise.
	(max_isa_vgprs): Likewise.