hppa64: Skip/xfail three ld tests on hppa*64*-*-*

The ver_def test fails because of the __text_seg and __data_seg
symbols in the dynamic symbol table.

The sec64k tests creates too many sections and fails.

The linux target doesn't currently have .data.rel.ro and fails the
regexp test for pr20995.

2026-01-24  John David Anglin  <danglin@gcc.gnu.org>

ld/testsuite/ChangeLog:

	* ld-elf/readelf.exp: Skip ver_def on hppa*64*-*-*.
	* ld-elf/sec64k.exp: Likewise.
	* ld-elf/shared.exp: xfail pr20995 on all OSes.