drm/amd/display: add pp to dc powerlevel enum translator

[why]
Add a switch statement to translate pp's powerlevel enum
to dc powerlevel statement enum
[how]
Add a translator function

Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>