powerpc/powernv: Data type unsigned int for PE number

This changes the data type of PE number from "int" to "unsigned int"
in order to match the fact PE number is never negative:

   * The number of PE to which the specified PCI device is attached.
   * The PE number map for SRIOV VFs.
   * The returned PE number from pnv_ioda_alloc_pe().
   * The returned PE number from pnv_ioda2_pick_m64_pe().

Suggested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-By: Alistair Popple <alistair@popple.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>