ariane: update PLIC and dts

add PLIC driver for Ariane and update dts

Signed-off-by: Nils Wistoff <nwistoff@iis.ee.ethz.ch>
Reviewed-by: Siwei Zhuang <siwei.zhuang@data61.csiro.au>

Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

review third-party license tags

Made third-party license tags more precise.

RISCV: Add support for Ariane SoC

Support Ariane SoC platform running on Genesys 2 FPGA board.