ARM: ixp4xx: fix ioport_unmap definition

An empty macro definition can cause unexpected behavior, in
case of the ixp4xx ioport_unmap, we get two warnings:

drivers/net/wireless/marvell/libertas/if_cs.c: In function 'if_cs_release':
drivers/net/wireless/marvell/libertas/if_cs.c:826:3: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
   ioport_unmap(card->iobase);
drivers/vfio/pci/vfio_pci_rdwr.c: In function 'vfio_pci_vga_rw':
drivers/vfio/pci/vfio_pci_rdwr.c:230:15: error: the omitted middle operand in ?: will always be 'true', suggest explicit middle operand [-Werror=parentheses]
   is_ioport ? ioport_unmap(iomem) : iounmap(iomem);

This uses an inline function to define the macro in a safer way.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Krzysztof Halasa <khalasa@piap.pl>