drm/vc4: Fix misleading name of the continuous flag.

The logic was all right in the end, the name was just backwards.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/20170627195839.3338-3-eric@anholt.net


Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>