pcnet-pci: Fix PIO word access to PROM Implement the various IO access widths according to the spec. This specifically unbreaks word and dword access to the PROM area that is mapped into IO space. It also drops redundant upper limit checks and spurious "return void". Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>