[GAS][AARCH64]Add group relocations to create PC-relative offset.

[GAS][AARCH64]Add group relocations to create PC-relative offset.

This is a patch to add the gas support for group relocations to create a
16, 32, 48, or 64 bit PC-relative offset inline.

The following relocations are added along with the test cases:
BFD_RELOC_AARCH64_MOVW_PREL_G0, BFD_RELOC_AARCH64_MOVW_PREL_G0_NC,
BFD_RELOC_AARCH64_MOVW_PREL_G1, BFD_RELOC_AARCH64_MOVW_PREL_G1_NC,
BFD_RELOC_AARCH64_MOVW_PREL_G2, BFD_RELOC_AARCH64_MOVW_PREL_G2_NC,
BFD_RELOC_AARCH64_MOVW_PREL_G3.

bfd/

2018-01-24  Renlin Li  <renlin.li@arm.com>

	* reloc.c: Add BFD_RELOC_AARCH64_MOVW_PREL_G0,
	BFD_RELOC_AARCH64_MOVW_PREL_G0_NC, BFD_RELOC_AARCH64_MOVW_PREL_G1,
	BFD_RELOC_AARCH64_MOVW_PREL_G1_NC, BFD_RELOC_AARCH64_MOVW_PREL_G2,
	BFD_RELOC_AARCH64_MOVW_PREL_G2_NC, BFD_RELOC_AARCH64_MOVW_PREL_G3.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.
	* elfnn-aarch64.c (elfNN_aarch64_howto_table): Add entries for
	BFD_RELOC_AARCH64_MOVW_PREL_G0, BFD_RELOC_AARCH64_MOVW_PREL_G0_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G1, BFD_RELOC_AARCH64_MOVW_PREL_G1_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G2, BFD_RELOC_AARCH64_MOVW_PREL_G2_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G3.

gas/

2018-01-24  Renlin Li  <renlin.li@arm.com>

	* config/tc-aarch64.c (reloc_table): add entries for
	BFD_RELOC_AARCH64_MOVW_PREL_G0, BFD_RELOC_AARCH64_MOVW_PREL_G0_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G1, BFD_RELOC_AARCH64_MOVW_PREL_G1_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G2, BFD_RELOC_AARCH64_MOVW_PREL_G2_NC,
	BFD_RELOC_AARCH64_MOVW_PREL_G3.
	(process_movw_reloc_info): Supports newly added MOVW_PREL relocations.
	(md_apply_fix): Likewise
	* testsuite/gas/aarch64/prel_g0.s: New.
	* testsuite/gas/aarch64/prel_g0.d: New.
	* testsuite/gas/aarch64/prel_g0_nc.s: New.
	* testsuite/gas/aarch64/prel_g0_nc.d: New.
	* testsuite/gas/aarch64/prel_g1.s: New.
	* testsuite/gas/aarch64/prel_g1.d: New.
	* testsuite/gas/aarch64/prel_g1_nc.s: New.
	* testsuite/gas/aarch64/prel_g1_nc.d: New.
	* testsuite/gas/aarch64/prel_g2.s: New.
	* testsuite/gas/aarch64/prel_g2.d: New.
	* testsuite/gas/aarch64/prel_g2_nc.s: New.
	* testsuite/gas/aarch64/prel_g2_nc.d: New.
	* testsuite/gas/aarch64/prel_g3.s: New.
	* testsuite/gas/aarch64/prel_g3.d: New.