drm/amdgpu: fix uninitialized scalar variable warning

Clear warning that field bp is uninitialized when
calling amdgpu_virt_ras_add_bps.

Signed-off-by: Tim Huang <Tim.Huang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>