PR26655, Power10 libstdc++.so R_PPC64_NONE dynamic relocs

PR26655, Power10 libstdc++.so R_PPC64_NONE dynamic relocs

Some of the powerpc64 code editing functions are better run after
dynamic symbols have stabilised in order to make proper decisions
based on SYMBOL_REFERENCES_LOCAL.  The dynamic symbols are processed
early in bfd_elf_size_dynamic_sections, before the backend
always_size_sections function is called.

One function, ppc64_elf_tls_setup must run before
bfd_elf_size_dynamic_sections because it changes dynamic symbols.
ppc64_elf_edit_opd and ppc64_elf_inline_plt can run early or late, I
think.  ppc64_elf_tls_optimize and ppc64_elf_edit_toc are better run
later.

So this patch arranges to call some edit functions later via
always_size_sections.

	PR 26655
bfd/
	* elf64-ppc.c (ppc64_elf_func_desc_adjust): Rename to..
	(ppc64_elf_edit): Call params->edit.
	(ppc64_elf_tls_setup): Don't call _bfd_elf_tls_setup.  Return a
	bfd_boolean.
	* elf64-ppc.h (struct ppc64_elf_params): Add "edit".
	(ppc64_elf_tls_setup): Update declaration.
ld/
	* emultempl/ppc64elf.em (params): Add ppc_edit.
	(ppc_before_allocation): Split off some edit functions to..
	(ppc_edit): ..this, new function.