board: rockchip: rk3399: Add myself as reviewer to MAINTAINERS

Add myself as a reviewer for RK3399 boards that I have and can help with
review and testing of defconfig and device tree changes.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/pine64/rockpro64_rk3399/MAINTAINERS b/board/pine64/rockpro64_rk3399/MAINTAINERS
index d9e11f4..42084ae 100644
--- a/board/pine64/rockpro64_rk3399/MAINTAINERS
+++ b/board/pine64/rockpro64_rk3399/MAINTAINERS
@@ -1,5 +1,6 @@
 ROCKPRO64
 M:	Jagan Teki <jagan@amarulasolutions.com>
+R:	Jonas Karlman <jonas@kwiboo.se>
 S:	Maintained
 F:	board/pine64/rockpro64_rk3399
 F:	include/configs/rockpro64_rk3399.h