drm/amdgpu: Remove unneeded semicolon

Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:2534:2-3: Unneeded semicolon

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>