drm/qxl: Replace drm_gem_object_reference/unreference() with _get/put()

Replace drm_gem_object_reference/unreference function with *_get/put()
suffixes, because it is shorter and consistent with the kernel
kref_get/put() functions. The following Coccinelle script was used:

@@
expression e;
@@

(
-drm_gem_object_reference(e);
+drm_gem_object_get(e);
|
-drm_gem_object_unreference(e);
+drm_gem_object_put(e);
|
-drm_gem_object_unreference_unlocked(e);
+drm_gem_object_put_unlocked(e);
)

Signed-off-by: Santha Meena Ramamoorthy <santhameena13@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1521570567-22519-1-git-send-email-santhameena13@gmail.com