drm/i915/cnl: only divide up base frequency with crystal source

We apply this logic to Gen9 as well. We didn't notice this issue as
most part we've encountered so far only use the crystal as source for
their timestamp registers.

Fixes: dab91783 ("drm/i915: expose command stream timestamp frequency to userspace")
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171113233455.12085-5-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/intel_device_info.c

@@ -403,15 +403,15 @@ static u32 read_timestamp_frequency(struct drm_i915_private *dev_priv)
 				freq = f24_mhz;
 				break;
 			}
-		}
 
-		/* Now figure out how the command stream's timestamp register
-		 * increments from this frequency (it might increment only
-		 * every few clock cycle).
+			/* Now figure out how the command stream's timestamp
+			 * register increments from this frequency (it might
+			 * increment only every few clock cycle).
 			 */
 			freq >>= 3 - ((rpm_config_reg &
 				       GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_MASK) >>
 				      GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_SHIFT);
+		}
 
 		return freq;
 	}