Add dptx firmware for rockchip rk3399

This dptx firmware is required by rk3399 Type-C DisplayPort controller.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Kyle McMartin <kyle@kernel.org>

WHENCE

@@ -3300,3 +3300,21 @@ General Public License.
 These firmware files are distributed in the hope that they will be useful, but
 are provided WITHOUT ANY WARRANTY, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTY
 OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+--------------------------------------------------------------------------
+
+Driver: rk3399-dptx - ROCKCHIP rk3399 dptx firmware
+
+File: rockchip/dptx.bin
+
+Licence: Redistributable.
+
+Rockchip Inc. grants permission to use and redistribute aforementioned firmware
+files for the use with devices containing Rockchip chipsets, but not as part of
+the Linux kernel or in any other form which would require these files themselves
+to be covered by the terms of the GNU General Public License or the GNU Lesser
+General Public License.
+
+These firmware files are distributed in the hope that they will be useful, but
+are provided WITHOUT ANY WARRANTY, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTY
+OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.