x86-64: Also generate unwind info for .plt.bnd

x86-64: Also generate unwind info for .plt.bnd

Also generate unwind info for the .plt.bnd section.  Sine it is the same
as unwind info for the .plt.got section, we use unwind info for the
.plt.got section to cover the the .plt.bnd section.

bfd/

	PR ld/21038
	* elf64-x86-64.c (elf_x86_64_link_hash_table): Add
	plt_bnd_eh_frame.
	(elf_x86_64_check_relocs): Create .eh_frame section for the
	.plt.bnd section.
	(elf_x86_64_size_dynamic_sections): Allocate and initialize
	.eh_frame section for the .plt.bnd section.
	(elf_x86_64_finish_dynamic_sections): Adjust .eh_frame section
	for the .plt.bnd section.

ld/

	PR ld/21038
	* testsuite/ld-x86-64/pr21038b.d: Updated.
	* testsuite/ld-x86-64/pr21038c.d: New file.
	* testsuite/ld-x86-64/pr21038c.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run pr21038c.