configure: expand ${prefix} in create_config

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/vl.c b/vl.c
index 7121cd0..6d08ec8 100644
--- a/vl.c
+++ b/vl.c
@@ -3423,7 +3423,7 @@
     }
     /* If all else fails use the install patch specified when building.  */
     if (!data_dir) {
-        data_dir = CONFIG_QEMU_SHAREDIR;
+        data_dir = CONFIG_QEMU_DATADIR;
     }
 
     /*