drm/i915/bxt: add missing DDI PLL registers to the state checking

Although we have a fixed setting for the PLL9 and EBB4 registers, it
still makes sense to check them together with the rest of PLL registers.

While at it also remove a redundant comment about 10 bit clock enabling.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 64041e7..1dbd957 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -372,7 +372,8 @@
 	uint32_t cfgcr1, cfgcr2;
 
 	/* bxt */
-	uint32_t ebb0, pll0, pll1, pll2, pll3, pll6, pll8, pll10, pcsdw12;
+	uint32_t ebb0, ebb4, pll0, pll1, pll2, pll3, pll6, pll8, pll9, pll10,
+		 pcsdw12;
 };
 
 struct intel_shared_dpll_config {