PR26656, power10 libstdc++.so segfault in __cxxabiv1::__cxa_throw

PR26656, power10 libstdc++.so segfault in __cxxabiv1::__cxa_throw

This adds missing support for a power10 version of the __tls_get_addr
call stub implementing DT_PPC64_OPT PPC64_OPT_TLS.  Without this,
power10 code using __tls_get_addr fails miserably at runtime unless
the --no-tls-get-addr-optimize option is given.

	PR 26656
	* elf64-ppc.c (plt_stub_size): Add "odd" param.  Use it with
	size_power10_offset rather than calculating from start of stub.
	Add size for notoc tls_get_addr_opt stub.
	(plt_stub_pad): Add "odd" param, pass to plt_stub_size.
	(build_tls_get_addr_head, build_tls_get_addr_tail): New functions.
	(build_tls_get_addr_stub): Delete.
	(ppc_build_one_stub): Use a temp for htab->params->stub_bfd.
	Emit notoc tls_get_addr_opt stub.  Move eh_frame code to
	suit.  Adjust code to use bfd_tls_get_addr_head/tail in place
	of build_tls_get_addr_stub.
	(ppc_size_one_stub): Size notoc tls_get_addr_opt stub.
	Adjust plt_stub_size and plt_stub_pad calls.  Correct "odd"
	when padding stub.  Size eh_frame for notoc stub too.
	Correct lr_restore value.
	(ppc64_elf_relocate_section): Don't skip over first insn of
	notoc tls_get_addr_opt stub.