drm/radeon/kms: add dpm support for rs780/rs880

This adds dpm support for rs780/rs880 asics.  This includes:
- clockgating
- dynamic engine clock scaling
- dynamic voltage scaling

set radeon.dpm=1 to enable it.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_pm.c

@@ -1030,6 +1030,13 @@ int radeon_pm_init(struct radeon_device *rdev)
 {
 	/* enable dpm on rv6xx+ */
 	switch (rdev->family) {
+	case CHIP_RS780:
+	case CHIP_RS880:
+		if (radeon_dpm == 1)
+			rdev->pm.pm_method = PM_METHOD_DPM;
+		else
+			rdev->pm.pm_method = PM_METHOD_PROFILE;
+		break;
 	default:
 		/* default to profile method */
 		rdev->pm.pm_method = PM_METHOD_PROFILE;