intel: Bump libdrm configure.ac requirement for the gen6 BLT ring support.
diff --git a/configure.ac b/configure.ac
index b451f7c..1b7372c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -972,7 +972,7 @@
 
 case $DRI_DIRS in
 *i915*|*i965*)
-    PKG_CHECK_MODULES([INTEL], [libdrm_intel >= 2.4.21])
+    PKG_CHECK_MODULES([INTEL], [libdrm_intel >= 2.4.23])
     ;;
 esac