drm/amdgpu: Remove unneeded semicolon in gfx_v10_0.c

Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c:1967:2-3: Unneeded semicolon

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>