Ensure 8-byte alignment for AArch64 stubs.

	PR 22903
bfd	* elfnn-aarch64.c (_bfd_aarch64_resize_stubs): Add 8 bytes for branch
	and nop instead of 4.
	(elfNN_arch64_build_stubs): Add nop after branch.  Increase size by
	8 instead of 4.

ld	* emultempl/aarch64elf.em (elf${ELFSIZE}_aarch64_add_stub_section):
	Give stub_sec 8 byte alignment.
	* emulparams/aarch64cloudabi.sh (NOP): Set to 0x1f2003d5.
	* emulparams/aarch64elf.sh (NOP): Likewise.
	* emulparams/aarch64elf32.sh (NOP): Likewise.
	* emulparams/aarch64fbsd.sh (NOP): Likewise.
	* emulparams/aarch64linux.sh (NOP): Likewise.
	* emulparams/aarch64linux32.sh (NOP): Likewise.
	* testsuite/ld-aarch64/erratum835769.d: Adjust for added nop.
	* testsuite/ld-aarch64/erratum843419.d: Likewise.
	* testsuite/ld-aarch64/farcall-b-defsym.d: Likewise.
	* testsuite/ld-aarch64/farcall-b-none-function.d: Likewise.
	* testsuite/ld-aarch64/farcall-b-plt.d: Likewise.
	* testsuite/ld-aarch64/farcall-b-section.d: Likewise.
	* testsuite/ld-aarch64/farcall-b.d: Likewise.
	* testsuite/ld-aarch64/farcall-back.d: Likewise.
	* testsuite/ld-aarch64/farcall-bl-defsym.d: Likewise.
	* testsuite/ld-aarch64/farcall-bl-none-function.d: Likewise.
	* testsuite/ld-aarch64/farcall-bl-plt.d: Likewise.
	* testsuite/ld-aarch64/farcall-bl-section.d: Likewise.
	* testsuite/ld-aarch64/farcall-bl.d: Likewise.