x86-64: Remove BND from 64-bit IBT PLT

x86-64: Remove BND from 64-bit IBT PLT

Since MPX support has been removed from x86-64 psABI, remove BND from
64-bit IBT PLT by using x32 IBT PLT.

bfd/

	PR ld/29851
	* elf64-x86-64.c (elf_x86_64_get_synthetic_symtab): Also check
	x32 IBT PLT for 64-bit.
	(elf_x86_64_link_setup_gnu_properties): Always use x32 IBT PLT.

ld/

	PR ld/29851
	* testsuite/ld-x86-64/ibt-plt-1.d: Updated.
	* testsuite/ld-x86-64/ibt-plt-2a.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2b.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2c.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2d.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3a.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3b.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3c.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3d.d: Likewise.
	* testsuite/ld-x86-64/plt-main-ibt-x32.dd: Moved to ...
	* testsuite/ld-x86-64/plt-main-ibt.dd: This.
	* testsuite/ld-x86-64/x86-64.exp: Don't use plt-main-ibt-x32.dd.