Use libdrm_amdgpu's amdgpu_get_marketing_name for the chipset name, or
"Unknown AMD Radeon GPU" as a fallback.

v2: Require libdrm_amdgpu >= 2.4.72 for amdgpu_get_marketing_name

Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)