ARM, MIPS, and RISCV can use the same implementation of
platform_sys_info(). PPC provides some extra information.
So keep it separate.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
(cherry picked from commit 6f7f47e8c0)
[Resolved conflicts due to api/ -> legacy_api/ directory rename in ci/master]
