ppc: Remove ARCH_P1022 support

With the last of the ARCH_P1022 platforms removed, finish removing the
rest of the platform support.

Cc: Priyanka Jain <priyanka.jain@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>