powerpc/powernv/pci: Move tce size parsing to pci-ioda-tce.c

Move it in with the rest of the TCE wrangling rather than carting around
a static prototype in pci-ioda.c

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200406030745.24595-7-oohall@gmail.com