unsigned int "version_minor" is always >= 0

Fixes the below:
drivers/gpu/drm/amd/amdgpu/amdgpu_rlc.c:534 amdgpu_gfx_rlc_init_microcode() warn: always true condition '(version_minor >= 0) => (0-u16max >= 0)'

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>