drm/savage: off by one in savage_bci_cmdbuf()

The > should be >= here so that we don't read beyond the end of the
dma->buflist[] array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180704094810.whrgn6jxe7uibnfv@kili.mountain