drm/amdgpu/gfx10: fix typo in gfx_v10_0_update_gfx_clock_gating()

Check was incorrectly converted to IP version checking.

Fixes: 4b0ad842 ("drm/amdgpu/gfx10: convert to IP version checking")
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>