drm/i915/psr: fix copy-paste error with setting of tp2_wakeup_time_us

Currently for the psr_table->tp2_tp3_wakeup_time case 3 there appears
to be a copy-paste error from the previous switch statement where
dev_priv->vbt.psr.tp1_wakeup_time_us is being assigned and I believe
it should be dev_priv->vbt.psr.tp2_tp3_wakeup_time_us that should be
assigned instead.

Detected by CoverityScan, CID#1470105 ("Copy-paste error")

Fixes: 77312ae8 ("drm/i915/psr: vbt change for psr")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180620132543.28092-1-colin.king@canonical.com

drivers/gpu/drm/i915/intel_bios.c

@@ -740,7 +740,7 @@ parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 			dev_priv->vbt.psr.tp2_tp3_wakeup_time_us = 100;
 			break;
 		case 3:
-			dev_priv->vbt.psr.tp1_wakeup_time_us = 0;
+			dev_priv->vbt.psr.tp2_tp3_wakeup_time_us = 0;
 			break;
 		default:
 			DRM_DEBUG_KMS("VBT tp2_tp3 wakeup time value %d is outside range[0-3], defaulting to max value 2500us\n",