bfd: fix build with --enable-targets=all in 32-bit hosts

bfd: fix build with --enable-targets=all in 32-bit hosts

This patch avoids for bpf_elf64_le_vec to be referenced in targmatch.h
when building a BFD without BFD64, resulting in an undefined symbol.
This was a regression introduced along with the BPF target.

bfd/ChangeLog:

2019-05-23  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* config.bfd (targ_cpu): Process bpf-*-none only if BFD64.
	* configure.ac: Set target_size=64 for bpf_elf64_le_vec and
	bpf_elf64_be_vec.
	* configure: Regenerate.