bfd: Add supported for LoongArch new relocations.

  Define new reloc types according to linker needs.

  include/elf/
    loongarch.h

  bfd/
    bfd-in2.h
    libbfd.h
    reloc.c
    elfnn-loongarch.c
    elfxx-loongarch.c
    elfxx-loongarch.h
7 files changed