drm/amdgpu: add helper to read UMA carveout info

drm/amdgpu: add helper to read UMA carveout info

Currently, the available UMA allocation configs in the integrated system
information table have not been parsed. Add a helper function to retrieve
and store these configs.

Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>