PowerPC64: fix build error on 32-bit hosts

PowerPC64: fix build error on 32-bit hosts

elf64-ppc.c:11673:33: error: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘bfd_vma’ {aka ‘long long unsigned int’} [-Werror=format=]
11673 |   fprintf (stderr, "offset = %#lx:", stub_entry->stub_offset);
      |                              ~~~^    ~~~~~~~~~~~~~~~~~~~~~~~
      |                                 |              |
      |                                 |              bfd_vma {aka long long unsigned int}
      |                                 long unsigned int
      |                              %#llx

	* elf64-ppc.c (dump_stub): Use BFD_VMA_FMT.