AArch64: Fix -Werror on build

This patch fixes a hardcoded `l` specifier on a `bfd_signed_vma`.
Instead this now uses BFD_VMA_FMT which fixes the build on 32 bit
hosts.

Committed under the obvious rule.

bfd/ChangeLog:

	PR ld/24373
	* elfnn-aarch64.c (_bfd_aarch64_erratum_843419_branch_to_stub):
	Fix print formatter.
2 files changed