mpc85xx: p2020: add missing symbols

mpc85xx: p2020: add missing symbols

Since kernel_oldconfig doesn't work properly with it, I ran that first
and then moved all the config symbols to config-6.6 and found the
differences.

Signed-off-by: Rosen Penev <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16847
Signed-off-by: Robert Marko <[email protected]>
(cherry picked from commit 22664498ebdd47aad9b15f62edbcaadd851fd62c)
Link: https://github.com/openwrt/openwrt/pull/17097
Signed-off-by: Petr Štetiar <[email protected]>