drm/radeon/dpm: fix spread spectrum setup (v2)

Need to check for engine and memory clock ss separately
and only enable dynamic ss if either of them are found.

This should fix systems which have a ss table, but do
not have entries for engine or memory.  On those systems
we may enable dynamic spread spectrum without enabling
it on the engine or memory clocks which can lead to a
hang in some cases.

fixes some systems reported here:
https://bugs.freedesktop.org/show_bug.cgi?id=66963

v2: fix typo

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/rv770_dpm.h b/drivers/gpu/drm/radeon/rv770_dpm.h
index 96b1b2a..9244eff 100644
--- a/drivers/gpu/drm/radeon/rv770_dpm.h
+++ b/drivers/gpu/drm/radeon/rv770_dpm.h
@@ -275,6 +275,7 @@
 void rv770_set_uvd_clock_after_set_eng_clock(struct radeon_device *rdev,
 					     struct radeon_ps *new_ps,
 					     struct radeon_ps *old_ps);
+void rv770_get_engine_memory_ss(struct radeon_device *rdev);
 
 /* smc */
 int rv770_read_smc_soft_register(struct radeon_device *rdev,