drm/amdgpu/gfx11: remove unneeded semicolon

Eliminate the following coccicheck warning:
./drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c:1222:2-3: Unneeded semicolon

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>