drm/amdgpu: use linux size macro to simplify ONE_Kib & One_Mib

replace internal size macro with linux size macro

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Tianci Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>