drm/amdgpu: Fix typo in IP discovery parsing

Fix a typo in parsing of the GC info table header when
reading the IP discovery table.

Fixes: 0e64c9aa

 ("drm/amdgpu: add type conversion for gc info")
Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>