aarch64: Remove macros for vld2[q]_lane Neon intrinsics

Remove macros for vld2[q]_lane Neon intrinsics. This is a preparatory
step before adding new modes for structures of Advanced SIMD vectors.

gcc/ChangeLog:

2021-08-12  Jonathan Wright  <jonathan.wright@arm.com>

	* config/aarch64/arm_neon.h (__LD2_LANE_FUNC): Delete.
	(__LD2Q_LANE_FUNC): Likewise.
	(vld2_lane_u8): Define without macro.
	(vld2_lane_u16): Likewise.
	(vld2_lane_u32): Likewise.
	(vld2_lane_u64): Likewise.
	(vld2_lane_s8): Likewise.
	(vld2_lane_s16): Likewise.
	(vld2_lane_s32): Likewise.
	(vld2_lane_s64): Likewise.
	(vld2_lane_f16): Likewise.
	(vld2_lane_f32): Likewise.
	(vld2_lane_f64): Likewise.
	(vld2_lane_p8): Likewise.
	(vld2_lane_p16): Likewise.
	(vld2_lane_p64): Likewise.
	(vld2q_lane_u8): Likewise.
	(vld2q_lane_u16): Likewise.
	(vld2q_lane_u32): Likewise.
	(vld2q_lane_u64): Likewise.
	(vld2q_lane_s8): Likewise.
	(vld2q_lane_s16): Likewise.
	(vld2q_lane_s32): Likewise.
	(vld2q_lane_s64): Likewise.
	(vld2q_lane_f16): Likewise.
	(vld2q_lane_f32): Likewise.
	(vld2q_lane_f64): Likewise.
	(vld2q_lane_p8): Likewise.
	(vld2q_lane_p16): Likewise.
	(vld2q_lane_p64): Likewise.
	(vld2_lane_bf16): Likewise.
	(vld2q_lane_bf16): Likewise.