drm/amdgpu: Program xcp_ctl registers as needed

XCP_CTL register is expected to be programmed by firmware. Under certain
conditions FW may not have programmed it correctly. As a workaround,
program it when FW has not programmed the right values.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>