nouveau: set lower_sub = true

Subtractions are already implemented as additions anyway.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
40 jobs for !2121 with nir_lower_sub in 18 minutes and 12 seconds (queued for 4 seconds)
detached
Status Name Job ID Coverage
  Containers
passed debian-10 #678003

00:00:22

passed debian-9 #678004

00:00:20

passed test-container:arm64 #678005
aarch64

00:00:22

 
  Build
passed meson-arm64 #678008

00:04:38

passed meson-armhf #678007

00:04:44

passed meson-clang #678010

00:07:25

passed meson-clover #678013

00:05:14

passed meson-clover-old-llvm #678014

00:07:00

passed meson-i386 #678016

00:04:05

passed meson-main #678006

00:11:39

passed meson-swr-glvnd #678009

00:04:46

passed meson-vulkan #678015

00:02:38

passed scons #678017

00:10:00

passed scons-old-llvm #678018

00:08:50

passed scons-swr #678011

00:06:33

passed scons-win64 #678012

00:06:54

 
  Test
passed arm64_a306_gles2 1/4 #678039
db410c

00:08:23

passed arm64_a306_gles2 2/4 #678040
db410c

00:10:41

passed arm64_a306_gles2 3/4 #678041
db410c

00:08:39

passed arm64_a306_gles2 4/4 #678042
db410c

00:04:23

passed arm64_a630_gles2 #678028
mesa-cheza

00:04:55

passed arm64_a630_gles31 1/4 #678029
mesa-cheza

00:06:45

passed arm64_a630_gles31 2/4 #678030
mesa-cheza

00:07:17

passed arm64_a630_gles31 3/4 #678031
mesa-cheza

00:07:31

passed arm64_a630_gles31 4/4 #678032
mesa-cheza

00:08:09

passed arm64_a630_gles3 1/6 #678033
mesa-cheza

00:04:25

passed arm64_a630_gles3 2/6 #678034
mesa-cheza

00:04:21

passed arm64_a630_gles3 3/6 #678035
mesa-cheza

00:03:51

passed arm64_a630_gles3 4/6 #678036
mesa-cheza

00:04:11

passed arm64_a630_gles3 5/6 #678037
mesa-cheza

00:04:09

passed arm64_a630_gles3 6/6 #678038
mesa-cheza

00:04:21

passed test-llvmpipe-gles2 1/4 #678019

00:03:21

passed test-llvmpipe-gles2 2/4 #678020

00:03:45

passed test-llvmpipe-gles2 3/4 #678021

00:03:27

passed test-llvmpipe-gles2 4/4 #678022

00:02:21

passed test-softpipe-gles2 1/4 #678023

00:01:02

passed test-softpipe-gles2 2/4 #678024

00:06:05

passed test-softpipe-gles2 3/4 #678025

00:06:05

passed test-softpipe-gles2 4/4 #678026

00:06:05

passed test-softpipe-gles3-limited #678027

00:04:07