drm/qxl: User page size macro for qxl release bo

Some architectures have different default page size, this patch
replaces hardcoded 4096 with PAGE_SIZE macro, since cmd bo size
is page aligned.

Signed-off-by: bibo mao <maobibo@loongson.cn>
Link: http://patchwork.freedesktop.org/patch/msgid/20210914062352.6102-1-maobibo@loongson.cn


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>