[GAS][ARM][2/3]Add SE_H shape to represent fp16 type.

[GAS][ARM][2/3]Add SE_H shape to represent fp16 type.

gas/

2016-02-24  Renlin Li  <renlin.li@arm.com>

	* config/tc-arm.c (NEON_ENC_TAB): Add fp16 instruction shape.
	(neon_shape_class): New SC_HALF.
	(neon_shape_el): New SE_H.
	(neon_shape_el_size): New size for SE_H.
	(N_F_ALL): New macro to aggregate N_F16, N_F32, N_64.
	(neon_select_shape): Add SE_H support code.
	(el_type_of_type_chk): Use N_F_ALL.
	(do_vfp_nsyn_cvt): Add SE_H shape support.
	(do_neon_cvtz): Likewise.
	(do_neon_cvt_1): Likewise.
	(do_neon_cvttb_1): Likewise.