powerpc mpc85xx: Fix infinite recursion in multiple bus methods

Similar to 68a3ff041129208ea98a3bd5142061176ab4165e, the default case
needs to call bus_generic_* to pass the request up the tree, not bus_*
which will just call this method again.

Fixes: 5a7e717fb790 powerpc mpc85xx: Use bus_generic_rman_*