[AArch64] Avoid GET_MODE_NUNITS in v8.4 support

[AArch64] Avoid GET_MODE_NUNITS in v8.4 support

This patch replaces GET_MODE_NUNITS in some of the v8.4 support
with equivalent values, in preparation for the switch to
NUM_POLY_INT_COEFFS==2.

2018-01-11  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* config/aarch64/aarch64-simd.md
	(aarch64_fml<f16mac1>l<f16quad>_low<mode>): Avoid GET_MODE_NUNITS.
	(aarch64_fml<f16mac1>l<f16quad>_high<mode>): Likewise.
	(aarch64_fml<f16mac1>l_lane_lowv2sf): Likewise.
	(aarch64_fml<f16mac1>l_lane_highv2sf): Likewise.
	(aarch64_fml<f16mac1>lq_laneq_lowv4sf): Likewise.
	(aarch64_fml<f16mac1>lq_laneq_highv4sf): Likewise.
	(aarch64_fml<f16mac1>l_laneq_lowv2sf): Likewise.
	(aarch64_fml<f16mac1>l_laneq_highv2sf): Likewise.
	(aarch64_fml<f16mac1>lq_lane_lowv4sf): Likewise.
	(aarch64_fml<f16mac1>lq_lane_highv4sf): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@256530 138bc75d-0d04-0410-961f-82ee72b054a4