drm/amdgpu/vcn2.5: fix PSP FW loading for the second instance

ucodes for instances are from different location

Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>