etnaviv: fix compile warnings in release build

[27/31] Compiling C object 'src/gallium/drivers/etnaviv/df32d18@@etnaviv@sta/etnaviv_compiler_nir.c.o'.
In file included from ../../src/gitlab_mesa/src/gallium/drivers/etnaviv/etnaviv_compiler_nir.c:552:
../../src/gitlab_mesa/src/gallium/drivers/etnaviv/etnaviv_compiler_nir_emit.h: In function 'ra_assign':
../../src/gitlab_mesa/src/gallium/drivers/etnaviv/etnaviv_compiler_nir_emit.h:903:9: warning: unused variable 'ok' [-Wunused-variable]
    bool ok = ra_allocate(g);
         ^~
../../src/gitlab_mesa/src/gallium/drivers/etnaviv/etnaviv_compiler_nir.c: In function 'etna_compile_shader_nir':
../../src/gitlab_mesa/src/gallium/drivers/etnaviv/etnaviv_compiler_nir.c:663:9: warning: unused variable 'ok' [-Wunused-variable]
    bool ok = emit_shader(c->nir, &options, &v->num_temps, &num_consts);
         ^~

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Jonathan Marek <jonathan@marek.ca>
13 jobs for !1645 with fix_compile_warnings in 12 minutes and 48 seconds (queued for 2 seconds)
detached
Status Name Job ID Coverage
  Containers Build
passed debian #498070

00:00:20

 
  Build+Test
passed meson-arm64 #498079

00:02:32

passed meson-armhf #498078

00:03:15

passed meson-clang #498072

00:09:21

passed meson-clover #498076

00:12:27

passed meson-i386 #498080

00:02:24

passed meson-main #498075

00:08:13

passed meson-swr-glvnd #498071

00:04:24

passed meson-vulkan #498077

00:04:10

passed scons-llvm #498082

00:06:03

passed scons-nollvm #498081

00:03:57

passed scons-swr #498073

00:06:17

passed scons-win64 #498074

00:11:00