vram_info table provides various vram information
including vram_vendor, vram_type, vram_width, etc.

v2: correct the calculation of vram_width
Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>