drm/amdgpu: Fix a memory leak

Fix a memory leak in amdgpu_fru_get_product_info().

Cc: Alex Deucher <Alexander.Deucher@amd.com>
Reported-by: Yang Wang <kevinyang.wang@amd.com>
Fixes: 0dbf2c56

 ("drm/amdgpu: Interpret IPMI data for product information (v2)")
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>