ltq-atm/ltq-ptm: re-enable/fix reset_ppe() functionality for VR9

ltq-atm/ltq-ptm: re-enable/fix reset_ppe() functionality for VR9

This patch re-enables the reset_ppe() functionality for VR9 targets by using
the new lantiq rcu subsystem. The reset sequence in the reset_ppe() function
was taken from the ppa datapath driver of lantiq UGW 7.4.1.

Additionally it adds the required reset definitions to the vr9 dtsi file.

It also prepares the reset_ppe() function calls for the other lantiq targets.

This feature is needed to be able to switch between ltq-atm/ltq-ptm driver
in ATM/PTM Auto-Mode at runtime.

Signed-off-by: Martin Schiller <ms@dev.tdt.de>