configure.ac: error out if building freedreno_kgsl without freedreno

The former is a subset of the latter. Error out early so the user is
aware that they are doing something very wrong.

Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
diff --git a/configure.ac b/configure.ac
index 7f76083..6e45fa8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -321,6 +321,11 @@
 	AC_DEFINE(HAVE_FREEDRENO, 1, [Have freedreno support])
 fi
 
+if test "x$FREEDRENO_KGSL" = xyes; then
+	if test "x$FREEDRENO" != xyes; then
+		AC_MSG_ERROR([Cannot enable freedreno KGSL interface if freedreno is disabled])
+	fi
+fi
 AM_CONDITIONAL(HAVE_FREEDRENO_KGSL, [test "x$FREEDRENO_KGSL" = xyes])
 if test "x$FREEDRENO_KGSL" = xyes; then
 	AC_DEFINE(HAVE_FREEDRENO_KGSL, 1, [Have freedreno support for KGSL kernel interface])