[BFD][AARCH64]Properly truncate no overflow checking relocation value for load/store immediate.

bfd/ChangeLog:

2018-06-20  Renlin Li  <renlin.li@arm.com>

	* elfxx-aarch64.c (_bfd_aarch64_elf_resolve_relocation): Use PG_OFFSET
	to resolve BFD_RELOC_AARCH64_TLSLD_LDST16_DTPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLD_LDST32_DTPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLD_LDST64_DTPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLD_LDST8_DTPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLE_LDST16_TPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLE_LDST32_TPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLE_LDST64_TPREL_LO12_NC,
	BFD_RELOC_AARCH64_TLSLE_LDST8_TPREL_LO12_NC.

ld/ChangeLog:

2018-06-20 Renlin Li  <renlin.li@arm.com>

	* testsuite/ld-aarch64/emit-relocs-115.d: Update test with new value.
	* testsuite/ld-aarch64/emit-relocs-534.d: Likewise.
	* testsuite/ld-aarch64/emit-relocs-555.d: Likewise.