powerpc/4xx/ocm: Fix phys_addr_t printf warnings

Currently the code produces several warnings, eg:

  arch/powerpc/platforms/4xx/ocm.c:240:38: error: format '%llx'
  expects argument of type 'long long unsigned int', but argument 3
  has type 'phys_addr_t {aka unsigned int}'
     seq_printf(m, "PhysAddr     : 0x%llx\n", ocm->phys);
                                   ~~~^     ~~~~~~~~~

Fix it by using the special %pa[p] format for printing phys_addr_t.
Note we need to pass the value by reference for the special specifier
to work.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>