configure: use HAVE_DRISW_KMS when handling kms swrast

Using HAVE_DRI2 to manage it seems counter-intuitive.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Rob Clark <robclark@freedesktop.org>
diff --git a/configure.ac b/configure.ac
index 027cfb1..98acfdd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -956,8 +956,13 @@
     dri_platform='drm' ;;
 esac
 
+if test "x$enable_dri" = xyes -a "x$dri_platform" = xdrm -a "x$have_libdrm" = xyes; then
+    have_drisw_kms='yes'
+fi
+
 AM_CONDITIONAL(HAVE_DRICOMMON, test "x$enable_dri" = xyes )
 AM_CONDITIONAL(HAVE_DRISW, test "x$enable_dri" = xyes )
+AM_CONDITIONAL(HAVE_DRISW_KMS, test "x$have_drisw_kms" = xyes )
 AM_CONDITIONAL(HAVE_DRI2, test "x$enable_dri" = xyes -a "x$dri_platform" = xdrm -a "x$have_libdrm" = xyes )
 AM_CONDITIONAL(HAVE_DRI3, test "x$enable_dri3" = xyes -a "x$dri_platform" = xdrm -a "x$have_libdrm" = xyes )
 AM_CONDITIONAL(HAVE_APPLEDRI, test "x$enable_dri" = xyes -a "x$dri_platform" = xapple )