drm/amdgpu: fix hpd bo size calculation error

the HPD bo size calculation error.
the "mem.size" can't present actual BO size all time.

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <Christian.Koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
2 files changed