POWERPC: overhaul with cpm2_map mechanism

Incorporating the new way of cpm2 immr access, introduced in the previous
patch, into CPM2 peripheral devices (fs_enet and cpm_uart). Both ppc and
powerpc approved working( real actions taken in powerpc only, ppc just
has a wrapper to keep init stuff consistent).

Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>