sh: use the the PCI channels's io_map_base

commit 43db595e8b5d78ce5ad2feab719814a76e3ad2e5
(sh: switch to GENERIC_PCI_IOMAP)
failed to take into account the PCI channels's
io_map_base for mapping IO BARs.
This also caused a new warning on sh.

Fix this, without re-introducing code duplication,
by setting NO_GENERIC_PCI_IOPORT_MAP
and supplying a sh-specific __pci_ioport_map.

Reported-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>