arm64: dts: rockchip: fix include reference

The way we handle include paths for DT has changed a bit, which
broke a file that had an unconventional way to reference a common
header file:

arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts:47:10: fatal error: include/dt-bindings/input/linux-event-codes.h: No such file or directory

This removes the leading "include/" from the path name, which fixes it.

Fixes: d5d332d3

 ("devicetree: Move include prefixes from arch to separate directory")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>