elf64-hppa: Replace plt_sec/plt_rel_sec with root.splt/root.srelplt

elf64-hppa: Replace plt_sec/plt_rel_sec with root.splt/root.srelplt

elf64-hppa should use root.splt and root.srelplt instead of plt_sec and
plt_rel_sec so that elflink.c can see splt and srelplt.  This fixed:

FAIL: ld-elf/pr19539

	* elf64-hppa.c (elf64_hppa_link_hash_table): Remove plt_sec and
	plt_rel_sec.
	(elf64_hppa_check_relocs): Replace plt_sec/plt_rel_sec with
	root.splt/root.srelplt.
	(elf64_hppa_create_dynamic_sections): Likewise.
	(elf64_hppa_size_dynamic_sections): Likewise.
	(elf64_hppa_finish_dynamic_symbol): Likewise.
	(elf_hppa_final_link): Likewise.
	(elf_hppa_final_link_relocate): Likewise.