powerpc/xmon: Realign paca dump fields

We've added some fields with longer names since we originally wrote
this, so the fields are no longer lined up. Adjust the widths to make
it all look nice again, eg:

  0:mon> dp
  paca for cpu 0x0 @ c000000001fa0000:
   possible                  = yes
   ...
   slb_shadow            [0] = 0xc000000008000000 0x400ea1b217000500
   slb_shadow            [1] = 0xd000000008000001 0x400d43642f000510
   ...
   rfi_flush_fallback_area   = c0000000fff80000   (0xcc8)
   ...
   accounting.starttime_user = 0x51582f07         (0xae8)

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