'set but unused' breaks drm-*-kmod

[Michael Butler]

Seems this new requirement breaks kmod builds too ..

The first of many errors was (I stopped chasing them all for lack of 
time) ..

--- amdgpu_cs.o ---
/usr/ports/graphics/drm-devel-kmod/work/drm-kmod-drm_v5.7.19_3/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c:1210:26: 
error: variable 'priority' set but not used 
[-Werror,-Wunused-but-set-variable]
        enum drm_sched_priority priority;
                                ^
1 error generated.
*** [amdgpu_cs.o] Error code 1