xf86drm: Fix ioctl struct clearing in drmAgpEnable

This one is a bit harder to notice.

Signed-off-by: Connor Behan <connor.behan@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>

xf86drm.c

@@ -1719,7 +1719,7 @@ int drmAgpEnable(int fd, unsigned long mode)
 {
     drm_agp_mode_t m;
 
-    memclear(mode);
+    memclear(m);
     m.mode = mode;
     if (drmIoctl(fd, DRM_IOCTL_AGP_ENABLE, &m))
 	return -errno;