PR26330, Malloc size error in objdump

	PR 26330
	* elf.c (_bfd_elf_get_symtab_upper_bound): Sanity check symbol table
	size against file size.  Correct LONG_MAX limit check.
	(_bfd_elf_get_dynamic_symtab_upper_bound): Likewise.
	(_bfd_elf_get_reloc_upper_bound): Don't check file size if writing.
	(_bfd_elf_get_dynamic_reloc_upper_bound): Likewise.
	* elf64-x86-64-.c (elf_x86_64_get_synthetic_symtab): Use
	bfd_malloc_and_get_section.