x86-64: Set tlsdesc_plt if GOT_TLS_GDESC_P is true

x86-64: Set tlsdesc_plt if GOT_TLS_GDESC_P is true

We need to set tlsdesc_plt for x86-64 if GOT_TLS_GDESC_P is true when
allocating dynamic relocations so that _bfd_x86_elf_size_dynamic_sections
will generate TLSDESC_PLT and TLSDESC_GOT in x86-64 output.

bfd/

	PR ld/22071
	* elfxx-x86.c (elf_x86_allocate_dynrelocs): Set tlsdesc_plt
	for x86-64 if GOT_TLS_GDESC_P is true.

ld/

	PR ld/22071
	* testsuite/ld-x86-64/pr22071.d: New file.
	* testsuite/ld-x86-64/pr22071.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run pr22071.