drm/qxl: make lots of things static.

/usr/lib/gcc/x86_64-linux-gnu/4.7/include/stddef.h:414:9: sparse: preprocessor token offsetof redefined
include/linux/stddef.h:17:9: this was the original definition
>> drivers/gpu/drm/qxl/qxl_drv.c:49:5: sparse: symbol 'qxl_modeset' was not declared. Should it be static?

Reported-by: kbuild test robot.
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
index d337da0..aa291d8a 100644
--- a/drivers/gpu/drm/qxl/qxl_drv.c
+++ b/drivers/gpu/drm/qxl/qxl_drv.c
@@ -46,7 +46,7 @@
 };
 MODULE_DEVICE_TABLE(pci, pciidlist);
 
-int qxl_modeset = -1;
+static int qxl_modeset = -1;
 
 MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
 module_param_named(modeset, qxl_modeset, int, 0400);