powerpc: mpc8xx: CPM parameter RAM can be anywhere

With relocation, CPM parameter RAM can be anywhere in the
dual port RAM, so don't split dual port RAM.

Remove dparam and dparam16 members of struct comm_proc

PROFF_XXX become offsets from the start of dual port RAM,
then they are now consistant with the offsets in RPBASE
registers.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>