ARM: iop32x: remove the platform

This was marked as unused in 5.19 and can now be removed

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Martin Michlmayr <tbm@cyrius.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Wolfram Sang <wsa@kernel.org> # for I2C
Signed-off-by: Arnd Bergmann <arnd@arndb.de>