drm/amd/pm/smu7: Remove non-functional SMU7 voltage dependency on DAL

drm/amd/pm/smu7: Remove non-functional SMU7 voltage dependency on DAL

It looks like this was written for an old version of DC (DAL)
and was never adapted afterwards. This was non-functional
because it relied on the "dal_power_level" field which was
never assigned anywhere in the code base.

Also, it was not implemented for CI ASICs.

Now superseded by the newer voltage dependency on display
clock table added by the previous commit, let's remove.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>