Fix an illegal memory access when accessing corrupt dynamic secondary relocations.

Fix an illegal memory access when accessing corrupt dynamic secondary relocations.

	PR 26931
	* elf-bfd.h (struct elf_backend_data): Add bfd_boolean field to
	slurp_secondary_relocs field.
	(_bfd_elf_slurp_secondary_reloc_section): Update prototype.
	* elf.c (_bfd_elf_slurp_secondary_reloc_section): Add new
	parameter.  Compute number of symbols based upon the new
	parameter.
	* elfcode.h (elf_slurp_reloc_table): Pass dynamic as new
	parameter.