[AArch64] BFD_RELOC_AARCH64_TLSLE_ADD_LO12 should enable overflow check

[AArch64] BFD_RELOC_AARCH64_TLSLE_ADD_LO12 should enable overflow check

BFD_RELOC_AARCH64_TLSLE_ADD_LO12 is used to generate simplest
one-instruction addressing for TLS LE model when tls size is smaller
4K. Linker need to make sure there is no TLS offset overflow.

2015-06-01  Jiong Wang  <jiong.wang@arm.com>

bfd/
  * elfnn-aarch64.c (elfNN_aarch64_howto_table): Set overflow type to
  complain_overflow_unsigned for BFD_RELOC_AARCH64_TLSLE_ADD_LO12.
  * elfxx-aarch64.c (_bfd_aarch64_elf_resolve_relocation): Don't use
  PGOFF for BFD_RELOC_AARCH64_TLSLE_ADD_LO12, that will mask off all
  potential high overflowed bits.

ld/testsuite/
  * ld-aarch64/tprel_add_lo12_overflow.s: New testcase.
  * ld-aarch64/tprel_add_lo12_overflow.d: Nex expectation file.
  * ld-aarch64/aarch64-elf.exp: Run new testcase.