hppa64: Implement support for DT_TEXTREL

This fixes ld-elf/pr19539, DT_TEXTREL in shared lib, and DT_TEXTREL
map file warning tests on hppa64.

2026-01-22  John David Anglin  <danglin@gcc.gnu.org>

bfd/ChangeLog:

	* elf64-hppa.c (allocate_dynrel_entries): Set DF_TEXTREL
	if it isn't already set and we encounter a relocation
	against a readonly section.
	(elf64_hppa_late_size_sections): Add DT_TEXTREL dynamic
	entry if we have relocs and DF_TEXTREL is set in info->flags.