drm/i915: switch KBL to the new stepping scheme

Add new symbolic names for revision ids, and convert KBL revids to use
them via the new stepping check macros.

This also fixes theoretical out of bounds access to kbl_revids array.

v3: upgrade dbg to warn on unknown revid (José)

v2: Rename stepping->step

Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/79b6c48211c6b214165391d350d556bad748f747.1616764798.git.jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index b2aede2..e2dd314 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -7233,12 +7233,12 @@ static void kbl_init_clock_gating(struct drm_i915_private *dev_priv)
 		   FBC_LLC_FULLY_OPEN);
 
 	/* WaDisableSDEUnitClockGating:kbl */
-	if (IS_KBL_GT_REVID(dev_priv, 0, KBL_REVID_B0))
+	if (IS_KBL_GT_STEP(dev_priv, 0, STEP_B0))
 		intel_uncore_write(&dev_priv->uncore, GEN8_UCGCTL6, intel_uncore_read(&dev_priv->uncore, GEN8_UCGCTL6) |
 			   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
 
 	/* WaDisableGamClockGating:kbl */
-	if (IS_KBL_GT_REVID(dev_priv, 0, KBL_REVID_B0))
+	if (IS_KBL_GT_STEP(dev_priv, 0, STEP_B0))
 		intel_uncore_write(&dev_priv->uncore, GEN6_UCGCTL1, intel_uncore_read(&dev_priv->uncore, GEN6_UCGCTL1) |
 			   GEN6_GAMUNIT_CLOCK_GATE_DISABLE);