drm/rockchip: Flip select/depends in Kconfig

Otherwise Kconfig gets confused and somehow ends up creating a 2nd drm
submenu. I couldn't find i915 because of this any more at first.

Cc: Andy Yan <andy.yan@rock-chips.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: linux-kbuild@vger.kernel.or
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>