powerpc/4xx/ocm: Fix fix for phys_addr_t printf warnings

My recent commit to fix the printf warnings in ocm.c got the format
specifier wrong, because I copied it from the documentation without
realising the square brackets are not meant as literals.

This results in the address being suffixed with a literal "[p]".

Actually tested this time:

  # cat info /sys/kernel/debug/ppc4xx_ocm
  PhysAddr     : 0x0000000400040000
  ...
  NC.PhysAddr  : 0x0000000400040000
  ...
  C.PhysAddr   : 0x0000000000000000

Fixes: 52b88fa1

 ("powerpc/4xx/ocm: Fix phys_addr_t printf warnings")
Reported-by: Christian Lamparter <chunkeey@gmail.com>
Tested-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>