BugLink: http://bugs.launchpad.net/bugs/1546572

This implements DPM for tonga.  DPM handles dynamic
clock and voltage scaling.

v2: merge all the patches related with tonga dpm
v3: merge dpm force level fix, cgs display fix, spelling fix
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Signed-off-by: yanyang1 <young.yang@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Eric Huang <JinHuiEric.Huang@amd.com>
(cherry picked from commit c82baa28)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>