drm/amdgpu/pm: Fix the power1_min_cap value

It's unreasonable to use 0 as the power1_min_cap when
OD is disabled. So, use the same lower limit as the value
used when OD is enabled.

Fixes: 19589468 ("drm/amd/pm: Support for getting power1_cap_min value")
Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>