drm/i915: Make SKL/KBL DPLL0 managed by the shared dpll code

Include DPLL0 in the managed dplls for SKL/KBL. While it has to be kept
enabled because of it driving CDCLK, it is better to special case that
inside the DPLL code than in the higher level.

v2: Use INTEL_DPLL_ALWAYS_ON flag. (Ander)

v3: Remove extremely paranoid WARN_ONs. (Maarten)
    Handle DPLL0 in skylake_get_ddi_pll() properly. (Ander)

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457451987-17466-14-git-send-email-ander.conselvan.de.oliveira@intel.com
diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.h b/drivers/gpu/drm/i915/intel_dpll_mgr.h
index adf4706..1d34147 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.h
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.h
@@ -54,9 +54,10 @@
 	DPLL_ID_LCPLL_2700 = 5,
 
 	/* skl */
-	DPLL_ID_SKL_DPLL1 = 0,
-	DPLL_ID_SKL_DPLL2 = 1,
-	DPLL_ID_SKL_DPLL3 = 2,
+	DPLL_ID_SKL_DPLL0 = 0,
+	DPLL_ID_SKL_DPLL1 = 1,
+	DPLL_ID_SKL_DPLL2 = 2,
+	DPLL_ID_SKL_DPLL3 = 3,
 };
 #define I915_NUM_PLLS 6