linux-firmware: rockchip: update dptx firmware to v2.9

This version firmware fixed the USB3 lanes config bug.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Kyle McMartin <kyle@kernel.org>

WHENCE

@@ -3307,6 +3307,6 @@ OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 Driver: rk3399-dptx - ROCKCHIP rk3399 dptx firmware
 
 File: rockchip/dptx.bin
-Version: 2.6
+Version: 2.9
 
 Licence: Redistributable. See LICENCE.rockchip for details.